We all know Plankton's ultimate goal is to rob the Krabby Patty secret formula, but does that goal make a bigger picture? Does Plankton has tendencies for world domination? And if he is, is he fascist?
Let's start with The SpongeBob SquarePants Movie. Plankton sets up Plan Z in which he steals King Neptune's crown so that Krabs remains frozen and steals the Krabby Patty formula. But then, Plankton give out bucket hats to customers which revealed that they were actually mind control helmets, turning citizens into zombies, with the only words "All Hail Plankton" being spoken and turning the Bikini Bottom into Planktopolis with Plankton's statute and name. Some one that would brainwash its citizens and forced build a city under their name is a fascist. What do you think?
Nazism basically means a far-right fascist ideology that incorporates biological racism and believes that the nazist's race is superior than the rest and tries to populate people within the Nazist's race and tries to exile or execute the others. Plankton doesn't see his own species as superior and he never has tried to kill people of other species.