Jocktopus Ludwig Vandenbush is a big simple-minded school bully who refers to himself in the third person, yet somewhere, underneath all the meat, is a brain and a heart longing to be expressed. He is generally one of the antagonists of the show, although he appears less evil in the second and third seasons.
Jocktopus plays on the football team with Pass, Punt, and Fumble. His girlfriend is Piranhica, a piranha from school. He thinks learning is "boring." Fish usually avoid him, due to him being the most aggressive and strongest fish. Apparently, he somewhat likes helping around the house with chores, according to his Fishbook profile.
When Mr. Baldwin checked the attendance, Jocktopus responded by saying "JOCKTOPUS!" ("Fish Out of Water"). Jocktopus was the MVP and was widely popular for his football skills. He even signed everyone's faces. When Milo tried out for the tryouts, Jocktopus complained and yelled that what Milo was doing was not football. He was angry that Coach Salmons saw agility and moves in Milo. Jocktopus said he had one thing to say to Milo when they win a game — it was "Jocktopus", and he cheered Milo like everyone else ("Underwater Boy"). Jocktopus had a major role when his birthday was up, and Milo, Oscar, and Bea needed to give him something. They decided to give him money. When Sunny gave him all his money for his birthday, he thought money was worthless paper and put Sunny inside a "punch later" box. When they found out Jocktopus hated money, they gave him Oscar instead. Jocktopus brought him to his locker. He later found out that Oscar was smart, so Oscar helped him with his bullying to avoid getting punched. When Oscar's program chose Albert Glass to be bullied, Jocktopus used the dice and notecard that Oscar gave him. Albert thought the message on the notecard was beautiful, but Jocktopus just beat him up. Mr. Baldwin spotted him and Jocktopus told Oscar what happened. Oscar stayed with him and refused to go back to Milo and Bea. However, when the program chose them, to protect his friends, Oscar saved them by making Jocktopus punch himself ("Happy Birthfish, Jocktopus").
When Milo told Oscar to laugh at everything, Oscar accidentally laughed at Jocktopus when he tripped. Jocktopus grabbed him and told him to meet him at 3:00 so he could pummel him. Milo came up with a plan to laugh at Jocktopus, so Oscar got wrapped up in Jocktopus' tentacles and started laughing crazily. Jocktopus said he was freaking him out. Then, everyone in the school started laughing at Jocktopus. He then swam away, crying ("Funny Fish"). When Oscar needed a new roomate, Jocktopus said he needed a new roomate because he broke his other one, making Oscar immediately say "NEXT!" ("Dances with Wolf Fish").
Jocktopus was once beating up Albert and made fun of him. Milo, Oscar, and Bea felt bad for him, so Milo tapped Jocktopus on the back and told him it was not cool to do this. Jocktopus punched Milo out of the tank. Later, everyone gathered around to see Jocktopus putting Albert into a lightbulb. Then Milo comes in with his ninja and the ninja overpowers Jocktopus. Jocktopus was put into a glass bowl for having bad behavior. When Oscar later mentioned that Milo was acting worse than Jocktopus, Jocktopus agreed, saying he was never as bad as Milo ("Milo Gets a Ninja"). When Albert had the dropsy, Jocktopus got balloons with Albert's face drawn on them and promised to punch the balloons instead of him ("Dropsy!").
When Milo asked the boys what the most radicalist thing they could think of was, Jocktopus said, "JOCKTOPUS!". When Clamantha disguised herself as a boy to spy on the other boys, she got spotted by Jocktopus, who picked her up and threw her out of the window. At the end of the episode, Jocktopus and Piranhica became the homecoming King and Queen, and both kissed on top of the float ("Fish Floaters"). When Oscar, Milo, and Bea had to rush to school in time for Oscar's attendance award, they ran into Jocktopus, who was blocking the entrance and tying all eight of his shoes. When Oscar hesitated did not want to talk to Jocktopus, Bea spoke up and kindly tried to ask him to move away from the door. Jocktopus became furious and threw Bea, Oscar, and Milo out of the tank for no particular reason ("Run, Oscar, Run").
Jocktopus had a particularly large role in "Fish School Musical". When the play came up, Jocktopus was shown to be really nervous. He played Beastopus, the villain of the play. When his cue was up, he refused to go on, only to have Mr. Mussels push him onto the stage. When he started reading his lines, Pass, Punt, and Fumble started teasing him, which made him hesitate, but he kept going on anyway. After they teased him even more, Jocktopus threw Razor at the three of them which made Bea frustrated. So, Bea found a trapdoor on the stage and told Oscar to pull the rope when she told him to. Jocktopus did not fall in the first two times, so Oscar threw Milo onto Jocktopus, which made him fall down the trapdoor. Bea talked to Mr. Mussels, who told Bea that Jocktopus showed up to Mr. Mussels' door, and told him that he needed to be in the play. So, Mr. Mussels and Jocktopus secretly practiced for the play together, until Jocktopus was finally ready to perform. This made Bea feel bad, but before she could do anything, Jocktopus exploded out of the trapdoor, and started destroying the stage. Oscar trapped him in a cage, and Bea went over to Jocktopus later backstage. Jocktopus told Bea that his father's wish was for him to sing a song in a musical about potatoes. Bea asked Jocktopus why he wrecked the stage, and he told her that he tried his best to do good, but the words were too hard for him to remember. Bea then told Jocktopus to go back on the stage and finish the show. The two managed to sing very well together, and Jocktopus' father started crying at Jocktopus' singing. After the musical finished, Jocktopus' dad congratulated him, and told Jocktopus to "smash some nerds," which caused Jocktopus to destroy the stage again.
It is revealed that every Halloween, Jocktopus steals everyone's candy. This makes Oscar gather up everyone to trick-or-treat outside the tank. After getting loads of candy in their wagon, they notice that Jocktopus somehow caught them. They got rid of Jocktopus for a while by throwing some candy at a nearby shelf to distract him. The wagon that holds all the candy suddenly stops, and Milo notices that one of the tires had been pinched. He accuses Randy Pincherson of doing it, which was actually true, as Randy left a trail of candy so Jocktopus would find them. Randy said that Jocktopus promised him half of the candy that he finds. Jocktopus and his gang stole everyone's candy and took off with it. Jocktopus replaces the flat tire with Punt, one of his henchmen. Oscar, who has everyone inside the horse suit, leads them to Jocktopus and tells him to give their candy back. Bea, whose costume is a zombie, scares Jocktopus, and makes him hang on into the side of the wagon. Behind the wagon is a stampede of ants, who shred Jocktopus's hat. Oscar says they'll only save him if he promises to never steal their candy on Halloween again. Jocktopus promises, and they all survive by jumping from the shelf into the tank. Three and a half weeks later, Jocktopus now ruins every Fishgiving by stealing their turkey ("Halloween Haul").
Jocktopus is shown to be really good at dodgeball, knocking down everyone except Steve Jackson, who throws a dodgeball back at Jocktopus' team. When Albert Glass puts on Steve Jackson's hair gel, he hits Jocktopus with one dodgeball, making Coach Salmons notice Albert's skills ("Hairanoid").
Jocktopus and Milo seem to have a generally good relationship after season 2, such as when they are paired up to take care of a baby in "Assignment: Babies", and Jocktopus does not act negatively towards Milo. Milo also asks Jocktopus to hang out in "Algae Day", to which Jocktopus says that he can't, not because he dislikes Milo, but rather because he has to hang out with Piranhica. Their friendship was addressed the most in "Freshwater Five-O", when they both envisioned themselves as crime-fighting police officers and both complimented each others' badges. They worked together as a team to find a police officer's car in the episode.
Pirahnica is head over fins in love with Jocktopus, and they are seen together lots of times ("Queen Bea," "Happy Birthfish, Jocktopus," "Big Fish," "Two Clams in Love," "Merry Fishmas, Milo," "Bea Dates Milo"). Pirahnica calls him names like "Babe," "Honey," and "Big Dreamy Hunk." The two were crowned King and Queen of homecoming and kissed on top of a float ("Fish Floaters"). They were both seen kissing again at the movie theater ("Bea Dates Milo") and in "Fish Prom". The couple volunteered at a flower booth in "A Charity Fair to Remember".
Jocktopus interacts with Oscar way more than Milo and Bea. Oscar is, of course, terrified of him, and Jocktopus likes beating him up. Oscar isn't Jocktopus' friend, so Oscar later regrets it when he calls him his friend, and Jocktopus says he's not his friend and that he owns him ("Happy Birthfish, Jocktopus"). They meet again when Oscar laughs at him because of Milo's plan to get out a fight. After Jocktopus is embarrassed by the room of students laughing at him, he runs off.
Jocktopus' only friends besides Piranhica are Pass, Punt, and Fumble. However, Jocktopus seems to just use them for his bullying rather than actually hanging out with them. He used Punt as a spare tire and forced Fumble and Pass to carry a wagon cart full of candy ("Halloween Haul"). Throughout the entire "Potatoes for Winter" play, Pass, Punt, and Fumble teased and made fun of Jocktopus, which made him mad enough to wreck the stage ("Fish School Musical").
- His name is derived from "jock" and "octopus."
- It looks like he has seven tentacles, but he really has eight.
- His height differs in some episodes, like in one episode, when he is slightly shorter than Koi, but in "Fish Floaters" and other episodes, he is slightly taller than her.
- He has a big room inside of a tiny locker, where he practices his punching ("Happy Birthfish, Jocktopus").
- He's the quarterback in his football team ("Underwater Boy").
- The line Jocktopus uses when bullying is "Daah! Jocktopus is hitting you now!" ("Happy Birthfish, Jocktopus").
- Jocktopus's eighth arm is his favorite out of his other arms ("Milo Gets a Ninja").
- His full name is "Jocktopus Ludwig Vandenbush" ("Happy Birthfish, Jocktopus").
- Jocktopus is one of the characters that has his eyeballs pointing in opposite directions more often than other fish (Clamantha, Albert Glass, Koi).
- Jocktopus always speaks in the third person.
- Even though octopi are quite intelligent animals, Jocktopus is not very bright.