Onions are a common ingredient used on Krabby Patties. They first appear in the episode "Help Wanted." In the show, they are also commonly used to make characters cry for comedic effect.
They are typically purple and are circular. They are also known to cause bad breath and make people cry.
Role in series
SpongeBob adds extra onions to make a Crying Johnny for a customer.
SpongeBob uses onions as one of the ingredients for his sundae.
A running gag in the episode is Squidward crying upon hearing SpongeBob's reluctance to give up Mystery, only for it to be revealed that it is actually a bowl of onions causing his tears.
Squidward then makes a customer fall victim to this running gag.
SpongeBob uses two onion slices and throws them at Patrick's eyes for self-defense.
SpongeBob realizes that the onions have gone bad and throws them away, with most of them hitting Fuzzy Acorns.
Squidward scares his trick-or-treaters away with onions.
Patrick says to give others "the stink eye," showing onions in his eye, the smell of which driving others away.