Amnesia

A character gets amnesia and forgets who they are. Sometimes they think they're someone else. This is usually caused by a blow to the head, and a blow to the head is usually what fixes it.

The Addams Family

Appearances

The Dick Van Dyke Show: Season 3, episode 7, "Who and Where Was Antonio Stradivarius?" (1963). A hit on the head gives Rob amnesia, and he starts calling himself Antonio Stradivarius.
My Favorite Martian: Season 1, episode 18, "Who Am I?" (1964). A monkey wrench that Martin left suspended in mid-air drops on his head and gives him amnesia, making him forget that he's a martian.
The Addams Family: Season 1, episode 22, "Amnesia in the Addams Family" (1965). When Gomez accidentally hits himself in the head with two indian clubs during his new exercise routine, he loses not only his memory but his whole personality, making him act like a regular person.
The Munsters: Season 2, episode 9, "John Doe Munster" (1965). After a safe falls on Herman's head, he develops amnesia and gets picked up by the police.
My Mother the Car: Episode 17, "I Remember Mama, Why Can't You Remember Me?" (1965). When Dave and his mother/car get into a fender bender, mother loses her memory and doesn't remember Dave or who she is.
Gilligan's Island: Season 1, episode 30, "Forget Me Not" (1965). Some Navy ships are about to pass the island, and the Skipper is the only one who knows how to signal them, but Gilligan's usual clumsy antics cause the Skipper to hit his head and lose his memory. When the Professor tells the rest of the castaways that another blow to the head might snap the Skipper out of it, they all secretly plot to knock him upside the head.
Get Smart: Season 2, episode 23, "Where-What-How-Who Am I?" (1967).A KAOS doctor gives Max a pill that makes him lose his memory.
Mary Hartman, Mary Hartman: Season 2, episode 64 (1976). While Loretta is in a bar, waiting for a bus to Dayton to record an album, a local creep starts harassing her, and another patron comes to her defense. The bartender joins in, and in the chaos, Loretta gets hit with a chair and knocked out. When she comes to, she doesn't remember who she is.
Barney Miller: Season 4, episodes 16-17, "Eviction" (1978). A woman with amnesia is taken to the police station, and she and Deitrich become very close while he tries to help her find out who she is. When he finally discovers her identity, he's disappointed to learn that she's a nun.
Soap: Season 2, episode 6 (1978). Chester wakes up from a coma and can't remember who he is or who any of his family members are.
Diff'rent Strokes: Season 3, episode 4, "The Accident" (1980). While on his way home to celebrate his 50th birthday, Mr. Drummond's car is hit by a drunk driver. He suffers a concussion that gives him amnesia, and he doesn't remember his family.
Mork & Mindy: Season 4, episode 15, "I Don't Remember Mama" (1982). Orson erases Mork's memory in an attempt to keep him focused on his job instead of his family.
Night Court: Season 3, episode 19, "Monkey Business" (1986). A woman with amnesia appears in court because she couldn't pay cab fare, and Dan falls for her right away, and she starts to fall for him, then she remembers who she is and that she hates his guts.
ALF: Season 1, episodes 16-17, "Amnesia" (1987). Alf slips and hits his head, causing him to get amnesia and think he's an insurance agent.
The Nanny: Season 3, episode 21, "Where's the Pearls?" (1996). Fran gets in an accident in a cab and hits her head, causing her to temporarily lose her memory. She not only forgets who she is and who everyone she knows is, but also what happened to the priceless black pearl necklace she was attempting to deliver to Elizabeth Taylor.
The Nanny: Season 5, episode 10, "From Flushing with Love" (1997). Mr. Sheffield takes a tumble on a boat in Niagara Falls and can't remember who he is, so Niles tells him he's the butler.
3rd Rock from the Sun: Season 2, episode 13, "Proud Dick" (1997). Harry gets swept up by a tornado and hit on the head with a flower pot, which causes him to forget who he is and that he's an alien. He reads a logbook and discovers that the rest of the gang are aliens and is terrified.
Community: Season 4, episode 4, "Alternative History of the German Invasion" (2012). After Change stages a coup and almost blows up the school, he returns with a doctor, who tells the dean he has "Changnesia" and doesn't remember who he is or what he did. The Dean is dubious, but when Chang checks himself into jail, he realizes he must be telling the truth.
Curb Your Enthusiasm: Season 10, episode 10, "The Spite Store" (2020). Larry's former assistant, Alice, who suffered brain damage after choking on one of his scones, develops amnesia and has no memory of Larry or what happened, but when she visits Larry's spite coffee shop and orders a scone, it all comes rushing back.