Tom John is an olive-green trout who wears a lavender shirt with light-blue shorts and has a solid body. He also has olive green-golden fins and legs. His eyes are quite big and the pupil is small, but the surrounding area of the eye is golden-brown, and he has light tan-salmon lips.
In "Pizza Delivery," he is dark orange with light-orange fins, dark olive-green eyes, light greenish-gray lips, is a little more obese than in his other appearances, and wears a dark-purple shirt and dark-teal shorts. This variation of him appears again in "Senior Discount."
In "Patty Hype," he is shown to be a lighter shade of green.
In other appearances, he looks the same as his olive-green look but has a light-green face and has dark olive-green eyes.
He was named in the episode "Patty Hype". When he met up with Fred, they greeted each other with their first name. In "Wigstruck" he is seen in a movie where he is referred as John.
Tom John lives a good life and he enjoys being married to Martha. He is a recurring patron at the Krusty Krab and enjoys their food.
Despite his general kindness, he can become somewhat insane and mentally ill. Tom is shown to have an obsessive-compulsive disorder when it comes to the food and beverage industry. In some of his appearances he violently obsesses over food and becomes extremely nitpicky over the most minor inconveniences that his food or drinks have to offer.
In "Pizza Delivery," Tom John lashes out at SpongeBob for forgetting to bring him his drink (though it is implied that Mr. Krabs hung up the phone before Tom could finish his order) as an addition to his pizza order, thereafter angrily slamming the door on him.
In "Fools in April," Tom John panics over SpongeBob allegedly doing something to his drink, although he regains his sanity when it's revealed to be a simple prank of putting in just one ice cube when he actually asked for a couple.
In "No Weenies Allowed," Tom John berates SpongeBob for accidentally landing his feet in his two bowls of potato salad that took 3 days to make.
His violent obsession with food reaches its epitome in "Chocolate with Nuts," where Tom goes berserk and loses his sanity over a sales offering of chocolate bars and stalks SpongeBob and Patrick in pursuit of the chocolate.
The game SpongeBob: Krusty Cook-Off reveals that he hates pancakes and doesn't understand why people like them, due to them not being either pans nor cakes; just talking about pancakes sends him into a screaming rage.
Tom John's house is seen in the episode "Chocolate with Nuts."
Tom John receives severe facial injuries when Squidward slams the pizza box in his face towards the end of "Pizza Delivery."
Tom John is shown to have suffered a severe buttock injury sometime before or during the events of "I Had an Accident," as he is treated by the "Iron Butt," a device that restrains his buttocks to enforce its safety.
Tom John is one of Gary's victims in "Once Bitten," giving him zombie-like side effects in the process.
Tom John has held various occupation titles over his vast appearance history.
Attempted prison escape: Tom John is among the many inmates who attempt to break out of prison in "The Inmates of Summer."
Civil disobedience: Tom John is shown to join many riots with the other Bottomite fish. In "Bubble Buddy," he and a small group of protesters knock over the lifeguard stand to get back at Bubble Buddy.
Stalking: Throughout a majority of "Chocolate with Nuts," Tom John manically stalks SpongeBob and Patrick in pursuit of the chocolate bars they're selling.
Role in series
In "Pizza Delivery," Tom John is SpongeBob and Squidward's customer to whom they must deliver the Krusty Krab pizza. Once they finally arrive at his house, Tom John becomes furious with SpongeBob simply for forgetting to bring him his drink and therefore refuses to eat his pizza, criticizing the Krusty Krab's service. However, he receives his comeuppance when Squidward violently slams the pizza box in his face and force-feeds it to him.
In "Fools in April," Tom John is one of SpongeBob's prank victims; Tom requests two ice cubes for his drink, but—as a prank—SpongeBob only puts in one.
In "Bubble Buddy," Tom John joins the other Bottomites in attempting to pop Bubble Buddy in retaliation for his misdeeds.
In "Patty Hype," he and Fred neglect the Krusty Krab and instead go to the Shell Shack.
In "No Weenies Allowed," Tom John lashes out at SpongeBob for accidentally placing his feet in his family's two bowls of potato salad.
Tom John plays his most prominent role yet in "Chocolate with Nuts," where he exhibits a violent obsession with chocolate and chases after SpongeBob and Patrick in pursuit of it.
In "I Had an Accident," Tom John is shown to have underwent a severe buttock injury that lead him into a state of hospitalization, as the "Iron Butt" is shown treating him.
Tom John appears in "Fear of a Krabby Patty" when SpongeBob screams at all the Krabby Patty hallucinations in sight, with Tom's wife thinking that he did it because Tom's shirt was hideous.
In "Hocus Pocus," he was seen driving with Monroe crying, "I don't like pistachio!" Tom John replies tensely, "Then why did you ask for it?"
In "Roller Cowards," Tom John is seen standing in line for the bathroom right in front of SpongeBob and Patrick, expressing annoyance toward the duo's antics.
In "Breath of Fresh Squidward," he is shown to have a daughter, and is married to Sadie. When Squidward creepily asks how everything is, Tom John answers with "What do you mean?" in a very skeptical tone.
In "The Battle of Bikini Bottom," when Patrick is telling the story of the battle, Tom can be seen as part of the Blue (don't wash hands) Team.