It's hard to believe that it's been 30 years since "Big" came along and showed us what happens when a 12-year-old boy becomes an adult overnight. Spoiler alert: Adulthood isn't all it's cracked up to be.

To celebrate this *big* milestone, here are some fun facts you might not know about this beloved comedy.

1. Thanks to "Big," Penny Marshall became thew first woman to direct a movie that grossed more than $100 million.
2. Writer Anne Spielberg originally wrote the screenplay under the assumption that her brother Steven Spielberg would direct and that Harrison Ford would star.

3. Disappointed to learn than the actual "walking piano" at FAO Schwartz didn't have enough keys to play "Heart and Soul," Marshall turned to creator Remo Saraceni to design a new version that had three times as many keys.
4. Tom Hanks and Robert Loggia managed to perform the walking piano scene entirely on their own, despite the fact that stunt doubles were hired to assist them.

5. To help Hanks accurately portray a 12-year-old trapped in an adult's body, Marshall filmed test scenes with actor David Moscow playing the part of the older Josh so that Hanks could then imitate Moscow's mannerisms in the real scenes.

6. Moscow had to wear colored contacts in order to help him more closely resemble Hanks. Hanks, for his part, wore oversized shoes in order to better mimic Moscow's gait.7. Actress Frances Fisher was cast as Billy's mother, but her scenes were cut from the theatrical release and never surfaced until the extended edition DVD release.

8. At first, scheduling conflicts prevented Hanks from taking on the role of adult Josh, resulting in Robert De Niro being offered the role instead. However, De Niro's salary requirement was too high, and eventually Hanks became available.

9. John Travolta was also considered for the lead role. While Marshall herself was enthusiastic about the choice, 20th Century Fox apparently felt otherwise, given Travolta's recent string of box office disappointments.

10. A Hollywood urban legend claims that Marshall filmed an alternate ending where Elizabeth Perkins' character, Susan, uses the Zoltar machine to transform herself into a young girl and reunite with Josh. Despite rumors that this ending surfaced on the VHS release in New Zealand, it doesn't actually exist.11. "Big" was adapted into a Broadway musical in 1996. While it was nominated for five Tony Awards, the show was deemed too costly and closed by the end of the year after 193 performances.