Title: "MMO-rons"

Plot: SpongeBob and his friends are playing Bikini Bottom's hottest new MMORPG. SpongeBob wants to come with Squidward on a quest, but Squidward says that the quest is only for members of his very exclusive guild (so exclusive, in fact, that they never ever take new members). Later, SpongeBob finds Patrick and has to explain to him that (1) SpongeBob's avatar did not eat SpongeBob (since Patrick hears SpongeBob's voice coming out of his avatar's mouth), and (2) SpongeBob is not trapped in Patrick's computer, he's at the Krusty Krab playing the game during slow periods when there aren't as many customers now that the Krusty Krab has wifi. Eventually, SpongeBob, Patrick, Sandy and (reluctantly) Squidward form their own guild and go on an epic quest to defeat an extremely powerful monster that has only ever been defeated by one other player, who has since disappeared with nobody knowing the player's true identity. Finally, at the end of the episode, after SpongeBob and his friends have defeated the monster, they encounter the legendary player who had previously been the only one to successfully defeat said monster. SpongeBob says, "Oh [legendary player's username], kindly bestow upon us some of your infinite gameplaying wisdom, so that we may someday follow in your virtual footsteps as legendary [title of the game] players!" After a brief silence, the legendary player finally speaks and says... "Meow."

And of course, Plankton would also be playing the game, and he'd be a major griefer.