The Hamster Incident: You can put a hamster in a microwave and blow it up. While Nintendo initially missed this, they forced a removal in later cartridge runs once they realized what was possible.
"NES SCUMM": The game's engine, SCUMM (Script Creation Utility for Maniac Mansion), was mentioned in the credits as "NES SCUMM". Nintendo forced its removal because they thought the word "scumm" sounded offensive.
Suggestive Dialogue: Nurse Edna’s original dialogue was deemed too sexual. Lines like "lucky you aren't a boy" were changed to more "motherly" threats, and a "For a Good Time" message on a wall was changed to "Call Edna".
Art Censorship: A nude classical statue in the hallway was given a dress, and a poster that said "Disco Sucks!" was removed entirely.