He is a dark green pet worm with light yellow-green and black eyes. He has a black leash.
Mr. Doodles, like all worms, is an underwater equivalent of a dog, as snails are those to cats. He is not shown to be vicious like Guard Worms, he just likes to bark and be walked by his owner, Mr. Krabs. He is a good companion to have, as shown in "As Seen on TV" like all worms are to their fish owners.
He first appears in the episode "Sandy's Rocket" as one of the characters who gets trapped in a moon rock sack by SpongeBob and Patrick.
His name is revealed in his second appearance in "As Seen on TV," where it is shown that he enjoys sniffing things and taking walks.