Prof. Sherman Klump
- Acrofatic: During his exercising montage, he gains a realistic degree of agility.
- Big Eater
- Catchphrase: "Oh my goodness."
- Dogged Nice Guy: He has a history of being this.
- Embarrassing Nickname: "Joe College", courtesy of his brother, Ernie Klump.
- George Jetson Job Security: Sherman seems to be fired in each movie before being hired again later.
- Mama's Boy
- Morality Pet: He becomes this to Cletus in the sequel. Thanks to having more screen time, Cletus shows that he does love his son and that he's very proud of him.
- Nice Guy
- Southern-Fried Genius: A professor who develops serums which transform fat people into thin people, turn split personalities into physical beings, and reverse aging. He can even do complex arithmetic in his head.
- Straight Man: Debatably and most surely. Even though he's just as fat and kind of rugged looking as the rest of them, unlike how his enemy, Buddy Love looks, Sherman is the only one of all the Klumps who behaves most decent and most respectfully and is always good intentioned in all of his blunders.
- Took a Level in Dumbass: Played for Drama: By removing Love from his DNA triggered a deterioration of his brain. He can't teach his class, articulate his words, and is a bit of a bumbler. Towards the end of the movie, he loses his memory, and breaks up with Denise, not wanting to burden Denise by being dumb. He his able to recover his brilliance by reabsorbing Buddy.
- Virgin in a White Dress: Gender Inverted: Grandma Klump mentions that because "Sherman's never had relations", he can wear a white tuxedo.
Cletus "Papa" Klump
- Amazingly Embarrassing Parents: Cletus doesn't hold back his obnoxious personality even when company is over. It doesn't help that he is under the impression that Sherman is getting married to Carla when he brings her over for dinner.
- Appeal to Nature: He's angered by how everyone is trying to lose weight, because everyone is supposed to be different sizes.
- Berserk Button: Mentioning his performance issues in the bedroom.
- Big Eater: All of the Klump family are this, but he appears to be the biggest of them all, as indicated by his having the largest meal in his "retirement" dinner.
- Deadpan Snarker:
- Gasshole: A mild example; he's more acerbic than outright assholish, but he more than fits the gassy part of the trope. He openly demonstrates his gasshole tendencies on both family dinner scenes in the first movie, resorting to deliberately breaking wind and utterly destroying any tracks of conversation that preceded it. Much to Ernie Junior's vast amusement.
- Grumpy Old Man: Somewhat in the first film; a lot more pronounced in the second film, thanks to the combination of his getting laid off from his job, and his impotence.
- Jerkass: Mostly aimed towards his mother-in-law, though he tends to argue with his wife about minor things, and loudly proclaims his right to break wind at the table.
- Large Ham
- The Loins Sleep Tonight: A subplot of the second film involves his anxiety about aging and its effect on his bedroom life.
- Manchild: Cletus dresses like a gigantic toddler at home, and farts to troll his wife.
- Papa Wolf: When Jason reveals that Buddy Love is trying to kill Sherman, he reveals that he brought a knife.
- Potty Failure: When he craps his pants by accident after trying to fart in the first family dinner scene.
- Troll: Cletus is definitely one of these, whether it be insulting Grandma Klump or farting at the dinner table.
- Rambling Old Man Monologue: Sherman unwittingly sets him off on one after he mentions that he's trying to avoid the calories in the fat and skin of the chicken dinner they've prepared.
- Meaningful Name: "Klump" is German for a clumsy, rude, and fat person. Cletus certainly fits the bill.
Anna Pearl "Mama" Klump
The mother of the family who gets over excited.
- Amazingly Embarrassing Parents: She doesn't help matters when arguing with Cletus about where they Sherman and Carla will get married.
- Berserk Button: Cletus saying bad things about her mother and farting loudly during dinner.
- Catchphrase: "Fabulous!", "Sherman! Sherman! Sherman!" and "Hercules! Hercules! Hercules!" usually with her clapping.
- Large Ham
- Mama Bear: When Jason reveals that Buddy Love is trying to kill Sherman, she reveals that she brought her razor.
Ernie Klump Sr.
Sherman's brother, and the father of Ernie Jr.; unlike Sherman, he's proudly blue-collar and constantly jibes at his brother's college background, until the end of the second film.
- A Date with Rosie Palms: Ernie Klump reveals that he "can relate" to when Grandma "relates" to herself.
- The Generic Guy: He's the Klump family member who we know the least about, other than that he seemingly takes more after his father, whereas Sherman takes more after their mother. An off-hand comment to Grandma (and Ernie Jr.'s mother not being seen or mentioned in either film) also indicates that he's divorced.
- Large Ham
Anna's mother, and a very horny Grandma who is always at war with Cletus.
- Cool Old Lady: The way she pulls a dinner knife and prepares to throw it at Cletus, you'd better believe it.
- A Date with Rosie Palms: "Sometimes, when I'm alone, I relate to myself."
- Dirty Old Woman: While she talks about sex a lot in front of Carla in the first film, it's taken Up to Eleven in the second when she orders a stripper for Denise's batchelorette party, and then forces herself on Buddy when she mistakes him for said stripper.
- False Rape Accusation: After Grandma strips off her clothes, she threatens to scream if Buddy doesn't give her a kiss.
- Fan Disservice: That garage scene with Buddy.
- Jerkass: She could be considered one because of how she not only talks the most cross of all the Klumps, but also because she is the least classy and is most crude and vulgar of them all. Even with the way she always insults Cletus and making them verbally always at each other's throats trading back and forth personal insults which always bothers Anna (Sherman's mother.) Not to mention how vulgar she is by going as far as the stunt she pulls on Buddy Love thinking that he is a male stripper which actually is bad enough to gross out a vulgarly perverted man like him to the point of making him vomit. These along with all the examples with her show you that she has the least moral conduct of all the Klumps.
- Large Ham
- Rambling Old Man Monologue: Gender Inverted.
- Troll: Loves needling Cletus about his performance issues.
Ernie Klump Jr.
- Embarrassing Nickname: Mama Klump calls him "The Baby".
- The Hyena: While he's normally quiet, he'll be left in stitches when Cletus farts or when Grandma begins talking about having relations.
- Junior Counterpart: To Ernie Klump.
- The Last of These Is Not Like the Others: The only Klump family member not to be played by Eddie Murphy, instead being played by then-child actor Jamal Mixon.
- The Silent Bob: He has no dialogue in the first film, apart from laughing at his grandfather's flatulence. His only lines in the second film are "Hey, how come Uncle Sherman is talking funny?" and "Now, that's cool. That's real cool." In an extended version of the restaurant scene, he says "How are you doing, Mr Issac?"
- The Ace: He's got all of Sherman's intellect, and none of the qualities that hold Sherman back. Though in the second film, his occasionally acting like a dog occasionally proves troublesome, and ultimately leads to his downfall.
- Adaptational Villainy: In the original Buddy was pretty obnoxious and conceited but doesn't do anything villainous. In this film, Buddy starts out this way, but starts to become truly evil as the film progresses, eventually attempting to make the transformation stable and permanent which would cause Sherman's identity to be entirely consumed and replaced by that of Buddy (as opposed to Sherman's being killed outright).
- Evil Laugh: Has a very loud one that he lets out whenever one of his plans comes to fruition.
- The Hyena: Initially he acts like this deliberately so as to annoy Reggie Warrington, but soon starts doing it unironically, mostly whenever he gets one up on someone.
- Jerkass: Initially he's not so much this as brash and confident. As time goes on, however, he starts becoming more outright evil, to the point of eventually plotting to permanently change himself into Buddy.
- Large Ham: Just watch the scene where he throws a tantrum at Carla when he arrives to the club an hour late.
- No Indoor Voice: He speaks with a loud voice.
- Sexier Alter Ego: Like his 1960s counterpart, he's a lot more confident and outgoing. However, he also has the benefit of shedding over half of Sherman's body mass.
- Troll: Being Sherman's hedonistic id, it's not surprising that he takes pleasure in getting on peoples' nerves.
- Villain Protagonist: At first, until it becomes clear that he's a completely separate persona and plans to take over Sherman's life.
- Meaningful Name: Purty sounds a lot like "Pretty", which fits given how attractive she is.
- Punny Name: A little more on-the-nose than her 1960s counterpart, with her name being even closer to "Pretty".
- Put on a Bus: The second film indicates that she and Sherman decided that they were Better as Friends, and that she returned to Chicago.
- She's Got Legs: How the audience — and Sherman — is introduced to her, as we see from Sherman's POV as he looks up from the floor (where he was picking up a sweet wrapper) and looks up her legs to the rest of her body.
Sherman's girlfriend, and later fiancée and then wife, in the second film.
- Huge Guy, Tiny Girl: By the end of the second film, she gets married to Sherman, who weighs probably more than twice as much as she does.
- Male Gaze: Sherman stares at her cleavage at the beginning and he gets what appears to be an erection (which turns out to be Buddy erupting from his crotch).Reverend: If anyone knows why these two should not be married, let them speak now. Or forever hold his penis."
- Suspiciously Similar Substitute: Aside from one or two minor differences in her character and backstory — she's implied to have been a former childhood friend of Sherman's, and is a fellow professor instead of a grad student — she's essentially the same character, note-for-note as Carla.
- Unfazed Everyman: Gets along just fine with the obnoxious overweight Klump family.
- Berserk Button: Mentioning his unfortunate incident with Petey the hamster.
- Bestiality Is Depraved: Cruelly inverted with a giant hamster.
- Butt-Monkey: Mildly so in the first film, where this is limited to his unknowingly drinking coffee laced with hamster droppings and then getting a "The Reason You Suck" Speech from Buddy near the end. Much more pronounced in the second film, courtesy of his encounter with Petey.
- Deadpan Snarker: Shown in his first scene with Sherman, where
- Dean Bitterman: Zig-zagged; while he does show a lot of the jerkish qualities associated with this trope, most of the time it's aimed specifically at Sherman, mostly because of how many rich donors his mishaps have driven away.
- Jerkass: While he does acknowledge Sherman's ability as a scientist, he also doesn't hesitate to poke fun at his weight, or threaten to fire him.
- Jerk with a Heart of Gold: Despite this, he did ally with Sherman Klump to stop Buddy Love from stealing the patent for the fountain of youth formula in the climax of The Klumps.
- Professional Butt-Kisser: Harland Hartley actually calls him a "professional butt kisser."
- Butt-Monkey: Holds this role in the first film, where he gets taken on a dangerously fast ride through Hollywood Boulevard by Buddy as he reverts to Sherman, then gets locked in a storage closet by Buddy, and then gets involved in a punch-up with him at the end. Less so in the second film, where Dean Richmond more holds this role.
- Only Sane Man: Shares this role along with Carla in the first film, and Denise in the second. He's usually the person who points out the danger that Sherman's experiments are putting him in.
- Undying Loyalty: Helps Sherman out of the various problems he brought upon himself.
A loud and obnoxious insult comedian who performs at the nightclub "The Scream" who publicly humiliates Sherman for being fat.
- Berserk Button: He doesn't take kindly to being upstaged by Buddy Love.
- The Bully: Crosses the line from being a caustic comedian into this when he goes from quickly poking at people's flaws to insulting and belittling Sherman non-stop.
- Hypocrite: He loves making fun of people, but doesn't take kindly when people make fun of him.
- Jerkass: One could have argued that his insults were just him doing his job, but his behavior towards Sherman pushes him well into this trope.
- Large Ham: He's quite full of himself.
- Laser-Guided Karma: After needlessly embarrassing Sherman, he gets even when Buddy roasts him terribly before upstaging him live. Then when Reggie snaps, Buddy manages to overpower him and throws him into a piano.
- Meaningful Name: Named after Reginald Hudlin and his brother Warrington, who he allegedly had a falling out with after appearing in Boomerang.
- Nice Hat: It covers what Buddy Love calls his "shitlocks".
A crazy TV workout guy who is based on Richard Simmons.
- Catchphrase: "Yes, I can!" He encourages anybody who wants to lose weight to say this.
- Large Ham
- Nice Guy
- No Celebrities Were Harmed: Lance Perkins is a parody of Richard Simmons.
Grandma's boyfriend in the second film.
- The Voiceless: He has no dialogue.