Oh, Professor Plankton, Door-to-door salesman.
— Professor Plankton, "Mermaid Man vs. SpongeBob"

Professor Plankton is an alter-ego of Plankton who appears in the episode "Mermaid Man vs. SpongeBob."


Professor Plankton looks like Plankton, but he wears a dark yellow long-sleeved shirt, a red bow tie, a white undershirt, and a beige hat. He carries a wooden cane and a brown suitcase.

Role in episode

He visits Shady Shoals Rest Home to convince Mermaid Man and Barnacle Boy about his shampoo, by stating them that they need dandruff removal. They become convinced on the product, so he gives them dandruff control shampoo named "Prof. Plankton's Dandruff Control Shampoo" (revealed to be "Prof. Plankton's Mind Control Shampoo" later on).

He soon notices they are hypnotized by the shampoo, so he then he reveals the shampoo to be "Prof. Plankton's Mind Control Shampoo." Since they are already hypnotized, it is too late for them to take notice of the effects.
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