Kimchi

Chowder's best friend and pet, Kimchi is a floating stink cloud. Most people don't' want to be around him, but Chowder doesn't mind Kimchi's smell.

Appearence
Often mistaken for a fart cloud, Kimchi is actually swamp gas because he grew up in a swamp (inside an alligator to be precise), as revealed in the episode "My Big Fat Stinky Wedding". Kimchi looks like a greener version of "The Flying Nimbus Of Roshi" from Dragon Ball Z with eyes, and like the Flying Nimbus, Chowder can sit on him and can use him as transportation like Goku. It could be possible than the Flying Nimbus was inspiration for Kimchi.