|Color:||Brown or Green|
William "Billy" is a cameo character seen in many episodes. He is a little kid who is seen playing with Timmy and other kids. His name is revealed in the episode Squirrel Jokes. He likes to accompany his mom when she goes to the Barg'n Mart. He is not to be confused with Billy (Teenager).
Billy has 3 different appearances.
The first variation of Billy has brown skin. He wears a red shirt and a blue and yellow-striped beanie with a blue propeller on the top. This is the most common variation of Billy.
The second one has a yellow and green-striped shirt. He has green skin. This variation is only seen in the episode Pickles and Walking Small, although it is also seen in other episodes with a non-speaking role.
The third one was in the episode Professor Squidward, he was a teen (or adult) and his name was revealed when he wrote it on the chalkboard.
However, all of these Billys may be different people.
 Friends and enemies
Billy has many friends and enemies. The reasons why are in this list.
- Timmy: He is seen playing with him always. He went with him to the Krusty Krab in the episode Krabby Land. Because they are half-brothers.
- Mini Squidward same reason why everybody else likes him.
- Squidward: He kicked Squidward on his tentacle because he teased him for losing the Skill Crane challenge.
- Mr. Krabs: Because of Krabby Land.
- Bubble Bass: Same reason why everybody else hates him.
- There is another Billy as on Professor Squidward