One major part of the show's running storyline is a falling-out between Kevin and Winnie, who becomes a background character for several months until she and Kevin reconcile. As a result, the primary reason for this part of the storyline was that actress Danica McKellar had a growth spurt, and she and star Fred Savage, already shorter than McKellar, didn't look right standing together. The characters reconciled after Savage began to catch up in height.
At the end of the episode of the finale, the voice of the narrator's kid at the end is Daniel Stern's son Henry - the producers wanted them to end the show talking to each other.
Actor Jason Hervey said that the scenes where he inched the car forward as Kevin tries to get in happened because his older brother did the same thing with him.
An actual narrator on-set was reading aloud the voiceover lines to make it easier for Fred Savage to react to the voiceover dialogue.
Fred Savage came to the attention of the show's casting directors through his roles in Vice Versa (1988) and The Princess Bride (1987). Not hearing of either movie, the producers obtained a rough cut of Vice Versa and cast Savage primarily due to his performance in the film.