He runs the Krusty Krab in the Mr. Plankton universe.
His success would lead to him leaving Karen for the female that main-universe Mr. Krabs marries. Mr. Plankton and this female have Pearl Plankton. Mr. Plankton then hires exactly the same people as main universe Mr. Krabs to get him where he is today.
He appears in a photo, in which he wears a swimsuit, with his daughter when Plankton first arrives in Mr. Plankton's universe.
He is later mentioned and referred to by numerous characters because they think that Plankton is him.