Over 400 celebrities have guest starred on Sesame Street, including actors, musicians, writers, politicians and athletes. The upcoming 40th season will feature appearances by Adam Sandler, Matthew Fox, Ricky Gervais, Judah Friedlander, both Gyllenhaals, Paul Rudd and Michelle Obama. Here are a few memorable guest spots from the first 39 years.

1. James Earl Jones Scares Your Children

In Sesame Street's second episode, James Earl Jones became the first celebrity guest (which was no surprise, since he was a student of Will Lee, Sesame's Mr. Hooper). Although having a big star like Jones is no shocker, what's strange is how he appeared. In a close-up of Jones' shiny, bald head, he counted to 10 and recited the alphabet in an intense, booming voice. The appeal, of course, was that a big star was participating in some basic preschool education, but the result was something truly terrifying to the toddlers in the audience (or at least to me, right now).

That didn't stop Sesame Street from bringing Jones back to host their 10th anniversary special, which featured less terror and more hair.

2. Ralph Nader: Consumer Advocate/Grammar Snob

Perhaps my favorite strange celebrity appearance is from a Sesame Street PBS pledge drive special from 1988 featuring Ralph Nader.

He joined Bob for a chorus of "The People in Your Neighborhood," singing, "A Consumer Advocate is a person in your neighborhood." When asked what a Consumer Advocate is, Nader explained by inspecting Bob's sweater, pointing out the shoddy workmanship, and destroying it in the process. While on the set, Nader initially refused to sing the song unless the lyrics were changed from "the people that you meet" to the more grammatically correct "the people whom you meet." Of course, they relented.

Ten years later, Nader attacked Sesame Street and PBS for including commercial sponsorship spots before and after each show.

3. Mr. Donahue Meets Mr. Snuffleupagus

In 1985, Phil Donahue appeared in one of the most famous Sesame Street episodes—the one where Mr. Snuffleupagus is revealed to the world. Donahue interviewed the people on Sesame Street to find out if they thought Snuffy—who had been on the show since the early 1970s, but perceived by the adults as an imaginary friend of Big Bird—was real. After the adults met Snuffy for the first time, Donahue had the pleasure of giving him a big ol' bear hug.

4. The Second Guy on the Moon

In 2005, Cookie Monster had it in his head that the moon is a giant cookie, which he plans on eating, thus altering the earth's tides forever. Luckily, Gordon was paid a visit by his close friend, "Second Guy on the Moon" Buzz Aldrin, who rained on Cookie Monster's parade by telling him the moon is just a big old rock. Though I didn't learn much about the moon, I did learn that it's very convenient to have famous friends.

5. The Micro Machines Guy

John Moschitta, Jr.—better known as either the fast-talking "FedEx Guy" or "Micro Machines Guy," depending on when you were born—appeared in several Sesame Street sketches. In this clip, he introduces his children, who each have extremely long names, one for every letter of the alphabet. It's unclear what lesson was being taught here.

6. Mayor Dinkins

Former New York Mayor Ed Koch made a cameo in The Muppets Take Manhattan, and current Mayor Mike Bloomberg appeared in A Muppets Christmas: Letters to Santa. But only one former Mayor appeared on Sesame Street. David Dinkins holds that honor, having appeared in 1992 to give Gordon the "Good Citizen Award." Congratulations, Gordon! It couldn't have happened to a nicer (or balder) guy.

7. Real Estate Tycoon Ronald Grump

grumpIt's rare for Sesame Street plots to involve an actual villain. Oscar fills that position most often, though he's more of a jerk than inherently evil. And we had the villainous Miss Finch and Huxley from Follow that Bird and Elmo in Grouchland, respectively. But one odd villain came to us by way of Joe Pesci, who portrayed the evil real estate tycoon Ronald Grump in the special, Sesame Street All-Star 25th Birthday: Stars and Street Forever! Pesci, donning the overblown Donald Trump toupee, decides to buy Sesame Street and replace it with high-rise condos. Naturally, his plans are foiled (by none other than Oscar the Grouch), and Sesame Street is safe from becoming a location on The Apprentice.

8. Neil Patrick Harris, Shoe Fairy

And no list of celebrity guests would be complete without Neil Patrick Harris' 2008 appearance as the Shoe Fairy.