He is friends with Oscar, Milo, and Albert Glass and plays strategy games with them often. Jumbo seems shy but friendly. Like Albert, Jumbo gets bullied by Jocktopus often. While Albert is a reading nerd, Jumbo is a math and science geek.
Jumbo had his first speaking role in "Milo Gets a Ninja."
He gets a big role in "Big Fish." When Milo wanted to be big and strong, Jumbo called Milo over when they were eating lunch. After Jumbo finished his pudding, he lead Milo to a rusty, old city, and thought he might be able to help him. He asked Milo if he knew Jumbo as a man of science, but Milo said he just thought he was a weirdo, and Jumbo told him that means he does not exaggerate. Jumbo then showed him the big tank and explained to Milo that he used to be tiny and was named "Shrimp Shrimp", so he went to the big tank, sat down on the chair, and grew big and strong. But he warned Milo to only sit there for 5.03 minutes, or there would be big concequences. After Milo did not listen and turned extremely huge, Jumbo told him he warned him about the consequences. He said there was only one thing that would make Milo small again, and that was the shrink tank. Jumbo then listened and danced to Oscar and Bea's "inspirational song" ("Big Fish"). When Milo sucked out all of the water in the tank, the whole class had to evacuate, with the exception of Jumbo, who stayed in the classroom to "analyze" the atmosphere ("Parasite Fright").
Jumbo fell for Milo's plan, along with all of the other students, when Milo told them about the "Cinco De Milo" party, which was only a scam to lure everyone outside of the tanks. At the party, Jumbo stated that the ratio of chips to dip was all wrong ("Pamela Hamster Returns").
In Oscar and Bea's morning announcements, Jumbo was their manager ("Good Morning, Freshwater"). When Randy was about to read Bea's diary in front of the whole school, Jumbo went to the auditorium because he thought they were supposed to show a movie ("Diary of a Lost Fish"). When Bea and Milo tried to help Oscar pick a club, they ended up walking to the map club, where there were only two people in the club: Jumbo Shrimp and Albert Glass ("We've Got Fish Spirit").
Jumbo was just as excited about going to Pupu Goodtimes amusement park as the other students. Jumbo told Oscar to join him and Albert in trying to beat a cup game to win a "Limited Edition Fork Saber." However, Jumbo's throws were all inaccurate, but very strong, and neither Jumbo, Oscar, or Albert knocked all the cups down ("Good Times at Pupu Goodtimes"). When Oscar told everyone to trick-or-treat outside the tank, Jumbo Shrimp and Albert joined their plan to get through Halloween without running into Jocktopus. Jumbo's costume was an owl ("Halloween Haul").
Jumbo and Albert tried to win the talent show together. When Clamantha and Shellsea had an argument in their dance group, Jumbo took Shellsea's side, only because he was scared of her ("Fish Talent Show").
When Milo and Oscar tried to figure out why Steve Jackson is so perfect, Jumbo and Albert told them that's the question all boys are trying to answer. Jumbo put down a projector and showed Milo and Oscar that Steve Jackson's perfection lies within his hair. When Steve walked past the boys, he accidentally dropped his hair gel, in which the boys took and all swam outside the school. Each of the boys put the gel on their hair, and they all became popular in Freshwater. When Jumbo was about to eat his pudding, he threw his spoon and dumped the pudding in his mouth, which made Esmargot and Clamantha drool. When the boys put on more hair gel in the bathroom, Oscar pointed out that they would probably run out of hair gel by the next morning. So Oscar put the hair gel in his locker. Later, when Oscar's hair was turning back to his normal hair-style, he went back to his locker to get more hair gel without anyone noticing. However, when Oscar went to his locker, he saw Albert and Jumbo trying to open Oscar's locker to get more hair gel as well. They all fought for it, and when Albert pulled out a string of Jumbo's hair, Jumbo became extremely angry, pulled out Albert and Oscar's hair, and put it on his hair ("Hairanoid").
One of Jumbo's biggest roles was in "Milo on the Lam." At the beginning of the morning, Jumbo was setting posters all over the halls, panicking about his lost sandwich. Later, when Milo was falsely accused of gluing Mr. Baldwin into his chair, he ran into Jumbo, who was the head hall monitor. Milo started asking him if he could help him. Jumbo told Milo that they might be friends, but he knew that Milo was a fugitive and was told to put him to detention. Milo then showed Jumbo a piece of the glue, which was cut into a lightning bolt shape by Albert Glass. Jumbo tried examining the glue piece, but he still couldn't tell who did it. Milo, deciding there was no other way, put on a fake beard to go into hiding, and asked Jumbo if he had any glue to stick the beard on. Jumbo told Milo that he had it in his pouch, although he noticed that he left it in the classroom. Milo then realized Jumbo Shrmip was the one who glued Mr. Baldwin to his chair, so he chased after Jumbo. Jumbo ran away to avoid detention and ended up in Fish Niagara Falls. Jumbo was up on top of the waterfall, and with Milo about to go to detention, begging him to confess, Jumbo surrendered and told everyone what really happened. In the morning, Jumbo was setting up posters of his lost sandwich, and was about to glue one of his posters in Baldwin's classroom. But he got distracted by how much glue was in his glue stick, and he dropped the glue in Baldwin's seat, causing Mr. Baldwin to sit on it afterwards. Mr. Baldwin heard the whole story, and when Jumbo told Baldwin he was accepting the fact that he was going to detention, Baldwin told Jumbo that he did not have to go because he is the one who ate his sandwich.
- He was first known as "Shrimp Shrimp" ("Big Fish").
- He is dating Angela as of "Unresolved Fishues".
- He gets very big and grows muscles when he gets angry, which is called "nerd rage."
- He still uses a pacifier ("Milo's Pony").
- In human form, Jumbo resembles Clarence from Clarence.