He has the same form as Plankton but has a large light brown beard, a light orange-yellow waistcoat, a white shirt, and black pants. SpongeBob thought he was really Dr. Peter Lankton when really he is Plankton.
When SpongeBob thinks he is seeing killer Krabby Patties, he goes to see Dr. Lankton. He is actually trying to get SpongeBob to tell him the secret formula. After many failed attempts, like using hypnotism and an ingredient combination, SpongeBob feels better and goes back to the Krusty Krab. Dr. Lankton yells "No! It's a lie! Therapy doesn't really work. You're still sick! Very, very sick!" but SpongeBob ignores him.
The name Peter Lankton has the "P" removed from "Plankton" and made into Peter.
There is such a last name called "Lankton;" thus it is not a completely made-up last name.