Mayo, short for Mayonnaise, is a sauce made of olive oil and eggs. It is sometimes used on a Krabby Patty. It first appears in the episode Hooky.
- In Nature Pants, SpongeBob gives Patrick a Mayo pot.
- In Hooky, according to Mr. Krabs, the only perspective of being in a Tuna can is the smell of a mayo.
- In Just One Bite, Harold has a lot of mayo on his patty and Squidward thinks it is disgusting.
- In Band Geeks, it is revealed that mayo is not an instrument. This has become a popular meme on the Internet.
- In Hocus Pocus, SpongeBob turned Patrick into mayo, after Patrick asked him to.
- In Planet of the Jellyfish, the Jellions' weakness is mayo. As a result, the replicas are not fond of it.