Many people overdo it with the drinking on St. Patrick's Day, but it's not always Guinness or Jameson that gets them into trouble. Sometimes it's the Shamrock Shake, McDonald's uniquely green and often elusive seasonal treat. Here’s the skinny on the 660-calorie indulgence.

1. The Shamrock Shake wasn't originally known as The Shamrock Shake.

The original name of the cult classic milkshake was slightly less alliterative. It was called the St. Patrick’s Day Green Milkshake. Catchy, no?

2. The Shamrock Shake is a charitable endeavor.

What does the Shamrock Shake have to do with the Ronald McDonald House and the Philadelphia Eagles? Everything, according to the fast food giant. When Eagles tight end Fred Hill’s daughter was being treated for leukemia in 1974, Fred and his wife spent a lot of time in waiting rooms and noticed many other emotionally depleted families doing the same. He thought it would be healthier for families if they had a place to call home while their children were being treated, so he used his football connections to get in touch with a local advertising agency that did work for Mickey D’s. They agreed to give profits from the Shamrock Shake toward a home near the Children’s Hospital in Philadelphia, which ended up becoming the first-ever Ronald McDonald House.

3. Uncle O'Grimacey used to be the Shamrock Shake's ambassador.

Back in the early ‘80s, a fairly offensive character named Uncle O’Grimacey was used to promote the seasonal shake.

4. No McDonald's restaurant is required to offer the Shamrock Shake.

In 2012, it was announced that, for the first time, the Shamrock Shake would be available in all McDonald's nationwide—but not all restaurants have to carry them. Regional managers decide whether their stores will carry the shakes each year.

5. Jimmy Fallon once depleted a New York City restaurant's entire Shamrock Shake supply.

If you’re a New Yorker and you didn’t get a much-craved Shamrock Shake in 2011, it’s probably Jimmy Fallon’s fault. When he caught wind that a Union Square Mickey D's had the elusive dessert, he totally cleaned them out—purchasing more than 100 shakes for his audience. New Yorkers were not pleased with Fallon.

6. The Shamrock Shake got an ice cream offshoot (that didn't fare so well).

Despite the smashing success of the shake, the Shamrock Sundae was a dismal failure. Introduced in 1980, it was discontinued after just a year. Apparently people prefer their unnaturally green desserts in shake form as opposed to scoop form. Though this year, they're trying again: in honor of the Shamrock Shake's 50th anniversary, McDonald's is also introducing an Oreo Shamrock McFlurry.

7. There have been many super-sized versions of the Shamrock Shake.

For a few years, a giant shake was poured into the Chicago River to help contribute to the green hue it’s dyed every year. A donation was also made to the Ronald McDonald House.

8. The McDonald's app will help you track down a Shamrock Shake.

Are you one of those unfortunate souls who has to hunt the shake down every year? McDonald's official app can help. In 2020, for the first time in three years, the Shamrock Shake will be offered at all McDonald's locations. If you're not sure of the nearest one near you, the McDonald's app has a full directory to help.

9. You can make your own Shamrock Shake at home.

If you still can’t find a shake, you have one other option: make your own.

10. In 2017, McDonald's engineered a special Shamrock Shake straw.

In 2017, McDonald's unveiled an amazing innovation for Shamrock Shake lovers: the STRAW. Short for Suction Tube for Reverse Axial Withdrawal, the STRAW was designed by real engineers at the aerospace and robotics engineering firms JACE and NK Labs—specifically with the Shamrock Shake in mind. What sets the device apart from conventional straws is the sharp bend in its shape and the three, eye-shaped holes in addition to the opening at the bottom end. The extra holes are positioned in a way that allows drinkers to take a sip of a new layered version of the frosty treat that’s equal parts top mint layer and bottom chocolate layer.

There’s no business like show business for having to leave your birth name behind. Movie stars throughout the past century have often adopted new names for a ton of reasons, from evading racial bias to pure whim. Here are 30 celebrities who you may not know changed their name, and who you may never look at the same way again.

1. Brad Pitt

One of the simplest stage name changes for one of the most famous men on the planet: It’s difficult to think of Brad Pitt as anything other than Brad Pitt, but the Oscar-winning star of Once Upon a Time in Hollywood was born William Bradley Pitt. Does Bill Pitt have the same ring to it?

2. Rihanna

Rihanna attends the Queen & Slim at AFI FEST 2019.

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Like Brad Pitt, the actor and singer from Barbados goes by her middle name professionally. She was born Robyn Rihanna Fenty. "I get kind of numb to Rihanna, Rihanna, Rihanna," she told Rolling Stone, noting that her close friends and family still call her by her first name. "When I hear Robyn, I pay attention."

3. Michael Caine

English actor Michael Caine, throwing a punch, August 1965

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Some actors streamline their names to be more memorable, which is what Maurice Micklewhite did when he became Michael Caine in 1954. He considered becoming Michael Scott (that’s what she said), but picked Caine because of Humphrey Bogart’s film The Caine Mutiny. In 2016, after a half-century of using the stage name and being unbelievably famous, Micklewhite finally legally changed his name to avoid hiccups at airports.

4. Audrey Hepburn

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The daughter of a Dutch noblewoman, Hepburn was born Audrey Kathleen Ruston and baptized as Edda Kathleen Hepburn-Ruston. Her professional name is sleeker, but it still would have been lovely to see "My Fair Lady starring Edda Hepburn-Ruston."

5. Cary Grant

Cary Grant is pictured in a publicity photo circa the 1940s.

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Hepburn’s co-star in Charade played a man with a lot of aliases, which had to have been at least a little familiar since Cary Grant began life as Archibald Leach. In 1931, Leach impressed the general manager of Paramount Pictures, B.P. Schulberg, enough to score a contract with the caveat that he pick a name that sounded more American. They came up with "Cary Grant" together.

6. Marilyn Monroe

A photo of Marilyn Monroe.

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Most everyone knows that Marilyn Monroe was born Norma Jeane Mortenson and that she was a natural brunette. Before acting, she modeled and sometimes flip-flopped her name, going as Jean Norman. But when she signed with 20th Century Fox, an executive there changed her name to "Marilyn" because she reminded him of Broadway actress Marilyn Miller. Monroe is Norma Jeane’s mother’s maiden name.

7. Albert Brooks

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Is there any need to explain why Albert Einstein changed his name to Albert Brooks? The legendary comedic factor and filmmaker was born into a showbiz family. His mom was a singer, and his father was a comedian on the radio. His brother, the late Bob Einstein, didn’t have the same need to change his name.

8. Tina Fey

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It seems appropriate that Tina Fey, who is famous for playing 30 Rock's Liz Lemon, is actually named Liz. Born Elizabeth Stamatina Fey, the former head writer of SNL and creator of 30 Rock has used the shortened form of her Greek middle name since early in her career, which kicked off in grand fashion with a banking commercial (and by "fashion" we mean: "Check out that swell vest").

9. Mindy Kaling

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Vera Mindy Chokalingam got her start doing stand-up, where she noticed that emcees would butcher her last name or mock it, so she shortened it. She also chose to go by her middle name, which her mother chose for her because she watched a lot of Mork & Mindy while she was pregnant.

10. Spike Lee

Spike Lee attends the 2020 Vanity Fair Oscar Party in Beverly Hills, California.

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The legendary filmmaker goes by Spike, but his birth name is Shelton, which is also his mother’s maiden name. She gave him the nickname "Spike" when he was a baby because he was tough. With that in mind, "Spike" has been his identity since almost the very beginning.

11. Natalie Portman

Natalie Portman attends the premiere of FOX's "Lucy In The Sky" in Los Angeles, California.

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Getting a professional start at a very young age, the Israel-born Neta-Lee Hershlag was an understudy on Broadway at 11 and starred in the hitman movie The Professional before she turned 13. To protect her family’s identity, she adopted her grandmother’s maiden name as her stage name.

12. Vin Diesel

Helen Mirren and Vin Diesel attend the 45th Chaplin Award Gala in New York City.

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“Vin Diesel? Of the New Brunswick Diesels?” It’s no surprise that “Vin Diesel” is a made-up name, but it’s interesting that Mark Sinclair didn’t come up with it because of his acting ambitions (even though he’s been acting since he was a child). Vin Diesel became Vin Diesel when he was a nightclub bouncer in New York City, which is why his name makes him sound like a nightclub bouncer. He’s the one who made us believe a bouncer could become an international movie star.

13. Helen Mirren

A name like Ilyena Lydia Vasilievna Mironov makes it sound like Helen Mirren was born to Russian royalty, but she was the child of an immigrant diplomat-turned-taxi driver in London. Her father, Vasily, and British mother, Kathleen, Anglicized the family name to Mirren in the 1950s. In 2003, after four decades of stellar work (plus Caligula), Mirren was made a Dame Commander of the Order of the British Empire, making her name even more impressive.

14. Sir Ben Kingsley

Sir Ben Kingsley arrives for the premiere of The Jungle Book at London's BFI IMAX.

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The celebrated actor changed his name, like so many actors do, as a survival technique. He wasn’t getting stage work under his birth name, Krishna Pandit Bhanji, but almost immediately got roles once he started going by Ben Kingsley. Unlike other actors, Kingsley has completely absorbed the stage name as his own, even signing his paintings with it.

15. Awkwafina

Awkwafina attends the 2020 Critics' Choice Awards in Santa Monica, California.

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The show is called Awkwafina is Nora From Queens because Awkwafina is Nora from Queens. Born Nora Lum, the rapper-turned-actor chose her stage name at 15 and views it as a full alter ego that embodies that wild, teenage energy that she learned to tone down in college. She carried the name over into her acting career for Ocean’s 8, Crazy Rich Asians, and The Farewell.

16. David Tennant

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The guy who became an actor because of Doctor Who—and then became The Tenth Doctor and married his favorite Doctor’s daughter, who played his cloned daughter in an episode of Doctor Who—was originally named David McDonald. He picked a stage name for the rather boring (and common) reason that there was already another actor named David McDonald in the union. Since Tennant started working at 16, he did the 1980s teen thing and named himself after Neil Tennant, the lead singer of the Pet Shop Boys.

17. Demi Moore

Demi Moore at a book signing of her memoir, Inside Out, at Barnes & Noble Union Square.

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Model Demi Gene Guynes changed her name when she married musician Freddy Moore at the age of 18 and held onto the name after their divorce a few years later, having used it for her role on General Hospital. There’s also some confusion about her first name, with some publications referring to her as Demitria despite Moore confirming that Demi is indeed her birth name. Of course, the more popular confusion about her first name can be cleared up like this: It’s pronounced Duh-Mee, not Dimmy.

18. Michael Keaton

Michael Keaton arrives at the 31st Santa Barbara International Film Festival in Santa Barbara, California.

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Batman star Michael Keaton is an example of an actor who needed to change his name because there was already an actor in the Screen Actors Guild with his birth name. Since actors’ names are their trademarks, it’d be like someone named Coca-Cola wanting to join the Soda Union. When you know that Keaton’s birth name is Michael Douglas, you can probably imagine why he had to pick a new moniker. He thought about becoming Michael Jackson. Ultimately, he went with “Keaton” and not for any particular reason (though there is one pervasive rumor—more on that below). Yet to this day, he has never legally changed it; he still goes by Michael Douglas in real life.

19. Diane Keaton

Diane Keaton at the 2020 Writers Guild Awards West Coast Ceremony in Beverly Hills, California.

Amy Sussman/Getty Images for WGAW

Ever since Michael Douglas changed his name to Michael Keaton, a rumor has floated around that he chose his now-famous name because of an attraction to Annie Hall actress and all-around titan Diane Keaton. Michael has dismissed the rumor, but not even Diane Keaton is actually a Keaton. The actress was born as Diane Hall; she chose her mother’s maiden name as her stage name. (And yes, the fact that she shares a surname with one of her most famous characters was very much intentional.)

20. Chevy Chase

Chevy Chase attends the premiere of The Last Movie Star in Hollywood, California.

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The former SNL star's nickname/stage name was given to him by his grandmother, who took it from the medieval English ballad "The Ballad of Chevy Chase." But Cornelius Crane Chase is named for his grandfather, Cornelius Vanderbilt Crane. It turns out that Chase's Community character’s father being named Cornelius was a nice inside joke.

21. Whoopi Goldberg

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Whoopi. Funny name for a funny person (and a serious actress with an EGOT under her belt). She started life as Caryn Elaine Johnson, and her silly nickname-turned-stage name means exactly what you think it means. “I was a bit of a farter!” Goldberg admitted during an interview with Graham Norton. “The theaters I was performing in were very small, so if you were gassy you had to walk away farting, and people would say I was like a Whoopee cushion.”

22. Fred Astaire

Fred Astaire and Ginger Rogers star in Carefree (1938).

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With a natural gift for performance, Frederick Austerlitz became the most famous American dancer of the 20th century. Like Spike Lee, it was Fred Astaire's mother who changed his name: When the family pursued a vaudeville career for their two children, she dropped the last name and replaced it with Astaire when he was 18.

23. Ginger Rogers

Astaire’s dance partner didn’t go by her birth name either: Virginia Katherine McMath changed her name after winning a Charleston (the dance, not the city) competition in 1925 and heading on tour. Ginger comes from her first name, and Rogers is her stepfather’s last name. She initially toured as "Ginger and her Redheads."

24. Queen Latifah

Queen Latifah attends the 2020 NBA All-Star Game in Chicago, Illinois.

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When Renaissance woman Queen Latifah released The Dana Owens Album in 2004, she was being true to her roots. Born Dana Elaine Owens in 1970, she changed her name when she was eight years old after finding Latifah (meaning delicate, sensitive, or kind) in a book of Arabic names at a time when others in her New Jersey neighborhood were switching to names with Arabic origins. When it came time to go pro, she added the “Queen” to evoke strength.

25. Jamie Foxx

Jamie Foxx attends a screening at Cinemark Baldwin Hills in Los Angeles, California.

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When Eric Marlon Bishop was starting out in comedy, he felt that female comics were put up on stage first since there were fewer of them. Looking for a somewhat androgynous name to misdirect emcees picking which stand-up hit the stage next, he chose Jamie, and he landed on Foxx as an homage to comic legend Red Foxx.

26. Bea Arthur

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Two things that might surprise you about The Golden Girls star: One, she was in the Marine Corps. Two, she was born Bernice Frankel. She married another Marine, Robert Aurthur, after she was honorably discharged, and modified that new last name to act as her stage name.

27. Lady Gaga

Lady Gaga attends the launch of Haus Laboratories in Santa Monica, California.

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It’s appropriately mysterious that there are conflicting accounts as to how Stefani Joanne Angelina Germanotta came by her stage name. The root of it stemmed from producer and then-boyfriend Rob Fusari comparing Germanotta’s sound to Queen’s "Radio Ga Ga." Fusari takes credit for the full name, saying his phone autocorrected “Radio” to “Lady” when he texted her one day. (He relayed this version of the story when he sued his ex back in 2010.) Gaga disputes that recollection, however; she says she liked how the stately elegance connoted by “Lady” offset and played with the craziness evoked by “Gaga.”

28. Jackie Chan

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Peerless as a modern martial arts star, Chan was born Chan Kong-sang in Hong Kong. He picked up "Jackie" while working in construction during college, where he worked with a man named Jack who thought highly enough of Chan to call him "Little Jack." More surprisingly, Chan’s mom called him Pao Pao ("Cannonball") as a baby, and it’s slightly disappointing that it didn’t became his stage name. Pao Pao Chan is an ideal martial arts movie star name. Jackie’s cool, too.

29. Portia De Rossi

Portia de Rossi attends the Nate and Jeremiah for Living Spaces Upholstery Collection Launch in Los Angeles, California.

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Usually aspiring actors will change a name they find clunky to something almost blandly inoffensive. The opposite is the case for Amanda Lee Rogers, who legally changed her name at the age of 15 to the Shakespearean "Portia." "In retrospect, I think it was largely due to my struggle about being gay," de Rossi told The Advocate. "Everything just didn’t fit, and I was trying to find things I could identify myself with, and it started with my name."

30. Kirk Douglas

Some of the time you learn an actor’s real name, and it makes perfect sense why they wanted to make the change. Other times you learn that Kirk Douglas was born Issur Danielovitch and wonder why he abandoned the raw power of that name. He grew up extremely poor but was able to attend the American Academy of the Dramatic Arts on scholarship where one of his classmates was Betty Joan Perske (a.k.a. Lauren Bacall).