Adaptational Personality Adjustment

Sometimes an adaptation features the character you know from the source material. Something feels off, though and you take a closer look. Maybe they like something different from their book, game, or epic saga counterpart.

Then it hits you; their personalities are different! They like various things or behave in a manner contrary to the source.

Generally, the Adaptational Personality Adjustment is more than simply making the character a Jerkass, a Badass, or a Wimp. It can shift them around, but are distinctly different from the source material.

Film

 * Harry Potter features this for some characters:
 * Owing to the other Gryffindors being Demoted to Extra, Dean sadly loses any mention of his drawing skills.
 * Book Seamus is an ordinary boy, characterized by his cheerful nature. Movie Seamus gets Running Gag of exploding anything that he points his wand at when performing a spell. Ron snarkily mentioned that he managed to turn water into tea, but there was too much smoke. Neville even gets in a line when he refuses to let Seamus countercurse his Leg Locker jinx because "you'll set my bloody kneecaps on fire!"
 * Book Dumbledore toes the line between Trickster Mentor, Manipulative Bastard and The Chessmaster. While characters lampshaded in The Deathly Hallows that they actually didn't really know him -- Harry realizes belatedly that Dumbledore's instructions to find the Horcruxes are very difficult while he and his friends are on the run, Abeforth had a falling out with him over -- Dumbledore was quite quirky and dangerous at the same time. He also rarely raises his voice, unless he is Surrounded by Idiots, aka confronting Cornelius Fudge. Two actors showed very different interpretations of him.
 * Richard Harris's Dumbledore was dry and serious. His robes are purple, and he walks with dignity. He gets in one quip about Bertie Botts's Every Flavor Beans at the end, when comforting Harry at the hospital.
 * Michael Gambon's Dumbledore in contrast, could be deadpan and snarky at times, with an Irish brogue to boot. He's also got a temper, as shown when manhandling Harry about putting his name in the Goblet of Fire and shouting at him. (In the book, "he asked calmly.") Unlike book Dumbledore, who begs for, movie Dumbledore says the same line "Severus, please" with calm and dignity, knowing.
 * How to Train Your Dragon (animation): This pretty much goes for any major character when making comparisons to the original source material:
 * Book Hiccup is a quiet, bookish dragon nerd kid that only snarks occasionally, while book Fishlegs spends his time snarking at the stupidity of the adults around them that are in charge of their lives. The film and franchise erverse their personalities where movie Fishlegs is the bookish dragon nerd kid and Hiccup is the Deadpan Snarker.
 * Book Toothless was a bratty housecat with wings. He spends most of his screen-time refusing to obey Hiccup, coercing fish and treats from him. Movie Toothless is more akin to a panther, and closer to Hiccup's riding dragon Windwalker as well as his elder companion The Wodensfang ; he is a deadly predator that never misses, but also willing to train Hiccup as much as Hiccup trains him.

Live-Action TV

 * Pretty Guardian Sailor Moon did this quite a bit:
 * Ami, in addition to her genius nature, is given No Social Skills to boot and a fear that her friends will leave her..
 * Princess Serenity, unlike the manga, isn't a carbon copy of . The first hint is actually that . Far from the sweet-natured princess that would sneak out to see Prince Endymion, this Princess Serenity is revealed to be.
 * Luna isn't quite as strict as she is in either the manga or the anime. Being a plushie cat, she can't scratch Usagi, and there's a hilarious scene where Luna fails to wake up Usagi for Senshi duties..
 * Minako is more serious than her manga counterpart; yes, that counts manga Minako's extensive Break the Cutie in her solo series' finale shortly before she moves to Tokyo to meet up with the girls. She thinks that Usagi is a "baka" if well-intentioned, and treats Rei with condescension for investigating her..
 * Zoicite in the manga was a Manipulative Bastard who brainwashed people to lure Sailor Moon into a trap, succeeding in capturing and nearly killing her. Here he's more of a Neutral Evil, who uses his piano to help ..
 * The never-released ToonMakers pilot of Sailor Moon featured this. Rather than Usagi an ordinary, ditzy teenage girl that happens to be a reincarnation for a Sailor Guardian, "Vicky" is the cover for Princess Sailor Moon after she and her friends escape from Beryl when they flee the Moon Kingdom, on Sailor Moon's wedding day no less. She hides sadness about leaving her home, her fiance Earth Prince Darien and her mother behind a smiling exterior and a desire for normal teenage girl things like dances and cosmetics. The other Senshi follow suit: Sailor Mars is a lot mellower than her original counterpart, asking her friends for fashion advice; Sailor Mercury loses the computer and her genius; Sailor Jupiter is more motherly; and Sailor Venus is less of a ditz, showing that she is a serious warrior in battle and a Handicapped Badass to boot.

Puppet Shows

 * When Sam Eagle plays Mr. Arrow in Muppet Treasure Island, he doesn't go with the script where the original Mr. Arrow was a bad-tempered alcoholic that drinks whiskey before going on-deck in a storm, at Long John Silver's inclination. No, this Mr. Arrow is anal-retentive and serious about rules, and he survives the movie due to spending several days testing out a "safe" lifeboat at Silver's suggestion..

Western Animation

 * Discussed in-universe during Avatar: The Last Airbender when the Gaang sees "The Ember Island Players". Aang complains that the bald woman portraying him shows a mischievous Avatar that can't resist playing jokes on his friends. Katara becomes prone to tears, Sokka is obsessed with food, Iroh is a Lazy Bum and so forth. Zuko, despite his protests to the contrary, is probably the most accurate in the Ember Island show, as he is dark and brooding and goes, "How can you say that?!" dramatically. Katara smirks when the actor proves her point.
 * The animated version of Bunnicula goes with this for all three of the main characters. Harold in the books is a lovable but observant dog that realizes that the title character is not a threat. Chester is paranoid that Bunnicula is evil but goes overboard in putting garlic everywhere. Meanwhile, the worst thing that book Bunnicula does is drain all the vegetables of their juice, something that his family rectifies by putting him on a strictly vegetable juice diet. Cartoon Harold is The Ditz being a dog with more floof than brain, Chester is a Nervous Wreck who is more than willing to work with Bunnicula to solve a problem, if not trusting him that much, and Bunnicula becomes a flying, shapeshifting prankster who will troll Chester if it amuses him.