Heroic Superheroes of the Deep is a Spongebob Crossover Season Four episode in Venturian Battle.
Two grave robbers break into Bikini Bottom Museum, and start a heist. A pirate security guard notices, and sounds the alarm. He questions the bank robbers, who turn out to have an alien gun, which they fire at him, turning him into a painting. The cat burglars drive off in a getaway Boat Mobile, stranding the pirate there, where a Venture version of the Sponge Bob theme plays.
Robert Jacob and his brothers decide to team up with Sponge Man and Star Man, the new superheroes in the underwater town after Mermaid Man and Barnacle Boy died, with the Jacobs joining to help build their reputation across the lands. Elsewhere, another burglar, Sheldon J. Plankton, obtains Jacob's fingerprints from his house and kidnaps senator Byron Fishy. He sells the fingerprints to the Fruit Deities, requesting a clean slate - a PC program that can wipe all traces of a person's criminal record - as payment.
The Fruits double-cross Plankton, but he uses Fishy's iPhone to alert the officers. Sponge Man and the cops arrive to find the libertarian, and then pursue some evil guys into the sewers while Plankton flees. The assailants capture Sponge and take him to Plankton, now revealed to be more than a bank robber, but a masked madman, who had set up his base of operation in the sewers. Sponge escapes and is found by Robert Jacob, whom Sponge Bob promotes to head gumshoe.
Plankton attacks the Bikini Bottom Stock Exchange, using Jacob's fingerprints in a transaction that leaves Robert bankrupt. He then murders a ton of fish. Robert, infuriated, is led into Plankton's trap. Plankton reveals that he intends to fulfill Dirty Bubble's quest to destroy Bikini Bottom before stealing Jacob's tech to Albert Mod. He then fights Robert, Robert delivering a crippling blow to Plankton's robot, before taking him to a heavily fortified jail. There, the inmates tell Plankton the story of Man Ray, who was born in the big house and cared for by a fellow scapegoat before escaping—the only felon to have ever done so.
While the Jacobs and Sponge Bob, Patrick, and Sandy celebrate at Glove World, Plankton lures the fuzz underground and baits and switches them into his cell. He assassinates Governor Pearl and forces Doctor Squid Ward, a squid atomic physicist he kidnapped from Rock Bottom, to convert the atomic furnace core into a nuke. Plankton uses the explosive to hold the city hostage and isolate Bikini Bottom from the planet. Plankton releases the from Bikini Bottom prison, initiating anarchy. The wealthy and strong have their property expropriated, are dragged from their houses, and are given show trials presided over by Stinky Flounder, where all are sentenced to death.
A month later, a disguised and reformed Dirty Bubble escapes from the penitentiary. He enlists the Jacobs, Sponge Man, Star Man, and Sandy to stop the explosive's explosion. Sponge Man gives the knights the Boat Mobile, tasking them with helping people evacuate. He asks the knights to leave Bikini Bottom, but Terrence Jacob refuses. After freeing the trapped constables, they clash with Plankton's soldiers and in the midst, Dirty Bubble squishes Plankton into a bloody pulp. However, Dirty Bubble is impaled by Karen, who aided his escapes from the correctional institutions before the other henchmen maimed him, requiring him to use a robot suit. She uses the remote detonator, but Tyler Jacob blocks her signal, preventing remote explosion. Karen leaves to find the explosive while Man Ray prepares to destroy Star Man. Robert returns on the Boat Mobile and saves Star Man by decapitating Man Ray with it. The heroes pursue Karen, hoping to bring the explosive back to the atomic pile privy where it can be stabilized. Karen's pickup truck crashes, but she remotely causes a tsunami and demolishes the atomic reactor outhouse before overriding her circuitry. With no way to stop the explosion, Mister Crabs uses the Boat Mobile to haul the explosive over the cove, where it explodes.
In a post credits scene, Robert gets all of his cash back, and swan dives in, and Mister Crabs is revealed to have survived the detonation, but turned into a living crab cake.