The lampreys are rather large and are faded purple.
Role in episode
The lampreys are first seen after Squidward pulls them out of the water when he and SpongeBob attempt to get Mr. Krabs' safe, which contains the Krabby Patty secret formula. The lampreys start to bite Squidward's hands and SpongeBob tells Squidward to use his teeth to pull them off. However, this only makes the lampreys bite his eyeballs instead, but eventually, the lampreys are pulled off for good.