Big is hardly the only age-changing movie that has ever been made. But even today, it remains one of the sub-genre's most enduring entries. Tom Hanks and director Penny Marshall were the two main reasons for the film's success, even though they only became involved in the project after other, bigger names (in 1988 anyway) backed out. Isn't that always the way?

1. HARRISON FORD WAS GOING TO STAR AS JOSH BASKIN, AND STEVEN SPIELBERG WAS GOING TO DIRECT.

Anne Spielberg, Steven’s sister, wrote the Big script with Gary Ross with the idea that Ford would star and the elder Spielberg would direct. When they dropped out, producer James L. Brooks presented the script to Penny Marshall.

2. THERE WERE A LOT OF MAJOR STARS BEING CONSIDERED FOR THE LEAD.

Tom Hanks was the first choice, but he was busy with other projects at the time. Marshall asked Kevin Costner, Warren Beatty, and Dennis Quaid, who all said no. Albert Brooks gave her the same answer, saying he didn’t want to play a kid. John Travolta really wanted to do it, but the studio didn't want Travolta ("at the time he was box office poison," Marshall wrote in her memoir). Sean Penn was deemed too young by Marshall. Gary Busey auditioned, but Marshall didn’t think he could pull off playing an adult.

3. ROBERT DE NIRO AGREED TO PLAY JOSH.

Wanting to make a family-friendly commercial film, De Niro at first accepted Marshall’s offer. De Niro and Jared Rushton, who played Josh’s childhood friend Billy, even hung out in Marshall’s driveway skateboarding and shooting hoops. However, De Niro’s $6 million price tag was ultimately too expensive, and after declining Marshall’s offer to pay him with her own salary, De Niro dropped out. But his short-lived attachment helped to raise the project's profile in Hollywood, so when approached about starring for a second time, Hanks said yes.

4. DEBRA WINGER TRIED TO CONVINCE MARSHALL TO CHANGE JOSH INTO A WOMAN.

The actress kept asking her director friend if the gender could be switched for the protagonist, but Marshall explained to Winger that she couldn’t see a way to make a 35-year-old man in a relationship with a 12-year-old girl not be “something from Penthouse or Hustler.”

5. IT WAS THE FIFTH AGE-CHANGE COMEDY TO COME OUT WITHIN ONE YEAR.

On October 2, 1987, the trend started with Like Father Like Son, the movie that swapped Dudley Moore and Kirk Cameron’s personalities. On December 23 in Italy, Da grande told the story of a nine-year-old boy having his wish to become an adult overnight come true (so that he could romance his teacher). On March 11, 1988, Judge Reinhold and Fred Savage unwittingly had their minds switched in Vice Versa. Three weeks later, 81-year-old George Burns’ age was inversed after a car crash in 18 Again! (A veteran producer said it was all a big coincidence.) Marshall didn’t know when she took the directing assignment that Big was not going to be an original idea on its June 3, 1988 release. She admitted that she read the scripts for Like Father Like Son and Vice Versa, and determined that their tones were different than Big’s.

6. HANKS AND ELIZABETH PERKINS HAD DOUBTS ABOUT THE MOVIE.

Because of the glut of similar movies that were beating them to the punch while they were shooting the movie, Perkins said that she and Hanks “looked at each other at one point like, ugh—this is going straight to video.”

7. YOU CAN FIND A ZOLTAR MACHINE AT RYE PLAYLAND. BUT NOT THAT ZOLTAR.

The scene at the end of the movie, where Josh finds the Zoltar machine again, was filmed at New York’s Rye Playland, but the machine was just a movie prop. In fact, if you went to the very spot where the machine was in the film today, you would find an Aquafina vending machine. But the park does have a Zoltar machine, albeit one that is notably different from the movie version—and located in a hut by the Dragon Coaster.

8. HANKS AND ROBERT LOGGIA DID THEIR OWN PIANO DANCING.

Robert Loggia portrayed MacMillan, who was modeled after then-FAO Schwarz CEO Peter L. Harris. After Loggia and Hanks spent months at home practicing the routine on huge cardboard piano keys, the two showed up for shooting and noticed dancers on standby. Motivated by the perceived slight, Loggia remembered telling the stunt men to “take a hike,” and performing the sequence with Hanks in “just about one take.”

9. THE CREATOR OF THE "WALKING PIANO" BUILT A BIGGER VERSION OF IT JUST FOR THE MOVIE.

Remo Saraceni built a 16-foot long, full three-octave piano so that Josh and MacMillan could play “Heart and Soul,” something that the six-and-a-half-foot long, one-octave "Walking Piano" on display at FAO Schwarz couldn’t accommodate. After the movie's success, Saraceni began selling the 16-foot version—for $15,000.

10. HANKS GOT TO SEE HOW A KID WOULD ACTUALLY BEHAVE IN HIS SCENES.

Penny Marshall videotaped David Moscow, the actor who played kid Josh, acting out all of the adult Josh scenes so that Hanks could study his mannerisms in each situation.

11. HANKS AND MOSCOW BOTH HAD TO CHANGE THEMSELVES IN ORDER TO PLAY THE SAME PERSON.

Moscow dyed his hair black and wore green contact lenses to look like a younger version of Hanks. Because his feet were growing at a rapid pace and he consequently wore ill-fitting shoes, Moscow had a weird duck-like gait, which led Hanks to ask for oversized shoes so that he could mimic Moscow's walk.

12. YOUNG JOSH HAD THE TIME OF HIS LIFE ON SET.

David Moscow got to stay up all night for the first time in his life when they shot the carnival scenes. He was able to ride all of the rides and eat a lot of cotton candy. Later, after shooting, Moscow and Jared Rushton became buddies in Los Angeles, surprising many L.A. onlookers who saw the two Big child stars hanging out together in real life.

13. JON LOVITZ GOT SICK DURING FILMING.

Lovitz, who played Josh's co-worker Scotty Brennen, came down with the flu in the midst of production. After a week of convalescence, Lovitz considered calling Marshall to say he was good to come back and finish filming before deciding that it was a “nothing” role. Once Big became a big hit, he felt like an “idiot.”

14. IN THE SCRIPT, SUSAN KISSES JOSH GOODBYE ON THE LIPS.

Since it was at the end of the film, after Susan discovers Josh’s real age, Marshall insisted that Elizabeth Perkins kiss him on the forehead instead.

15. PENNY MARSHALL MADE MOVIE HISTORY.

In her second movie directing assignment, Marshall became the first female director to ever direct a film that made more than $100 million at the box office.