Complex sentence: When Buster is the hospital he can't remember the fight he had with Lucille or his revelation that Oscar is his father this is a callback to when Micheal couldn't remember the events preceding his car accident My Mother the Car.
Split into simpler sentences: When Buster is in the hospital, he can't remember the fight he had with Lucille or his revelation that Oscar is his father. This is a callback to when Micheal couldn't remember the events preceding his car accident My Mother the Car.