Guard worm

Guard worms are large worms that guard various places in Bikini Bottom. They are the undersea equivalent of guard dogs and first appear in the episode "The Lost Mattress."

Description
They are usually light green and have silver spiked collars. In "Gary & Spot," the guard worm is light blue. In the episode "BlackJack," the guard worm's eyes are red, unlike every other appearance of guard worms.

Role in series
One appears in the episode "The Lost Mattress," named JK, where it is living in The Dump. attempts to have and  get mauled by the worm only for Squidward himself to fall victim to it each time.

Another appears in the episode "BlackJack," when SpongeBob's eponymous cousin has one guarding his front entrance.

In "Best Frenemies," one is guarding the Kelpshake store on the night and  try to steal the eponymous drink's formula.

There are various worms who work for the Bikini Bottom Police Department. In the episode "Slide Whistle Stooges," three guard worms are supporting the police to go against Squidward, but then attack a police officer when he insults them after they go wild from the terrible whistle sounds Squidward makes.

In "Toy Store of Doom," the manager has a guard worm to detect intruders prior to the closing of the Toy Barrel store. The worm narrowly manages to avoid catching SpongeBob and Patrick hiding in the doll houses. This worm is not mean or violent unlike the others that have been shown before.

In "Gary & Spot," a guard worm is one of and Spot's friends who gets locked in the pound.

Trivia

 * Their spiked collar represents the ones that dangerous dogs normally wear.