|Season 3, Episode 5|
|Air date||September 28, 1991|
Fourth of July
Zack sprains his knee before the big basketball game, and while in hospital learns that Lisa is a part-time candy-striper. However, he also learns that he will need surgery to repair his knee and worries that it may go wrong.
- Mark-Paul Gosselaar as Zack Morris
- Mario Lopez as A.C. Slater
- Dustin Diamond as Screech Powers
- Tiffani Thiessen as Kelly Kapowski
- Elizabeth Berkley as Jessie Spano
- Lark Voorhies as Lisa Turtle
- Dennis Haskins as Richard Belding
- Susan Beaubian as Dr. Turtle
In the episode, Zack accidentally undergoes genital reassignment surgery. Upon waking, he pledges to live his life to the fullest as a woman. Though the storyline was never addressed again (outside of a season four episode where Zack references having a labia), social conservatives were very angry and many stopped watching the show due to its positive portrayal of gender fluidity.