He first appeared in the episode, "Sandy's Rocket," as one of the characters who got trapped in a moon rock sack by SpongeBob and Patrick. His name was revealed in "As Seen on TV" (Which was also his last appearance and was never seen in any other episodes after that), where it is shown he enjoys to sniff things and take walks. He, like all worms, is an underwater equivalent to a dog, as snails are those to cats. Mr. Doodles is not shown to be vicious like Guard Worms, he just likes to bark and be walked by his owner (aka Mr. Krabs). He is a good companion to have, as shown in "As Seen on TV" (Last appearance), like all worms are to their fish owners.