Spot is the pet of Plankton, just like his owner he is a amoeba. Spot acts like a dog, as he barks and can wag his tail just like an actual dog does. Though the only thing that is strange is that even though Spot does act like a dog, in the SpongeBob universe, worms are considered to be the dogs, though it is possible that it differs for amoebas. Spot has so far only appeared in one episode, which was in the season 9 episode "Plankon's Pet." As many fans are wanting to see Spot return to the show, so it is very likely that Spot will return to the series (as he has caught much attention from SpongeBob SquarePants fans). So far though Spot has only appeared once, as said before he is a very well known character now.