Translating a character from page to screen is a tricky deal. Scripts and stories go through so many changes during their development - due to Executive Meddling, Wag the Director or writers changing their minds. But a lot of the time, the script won't change. Rather, an actor's interpretation of a character causes a change.
A character who was written to be a villain or Jerkass gets made more sympathetic due to the actor's portrayal. A Jerkass can turn into a Jerkass Woobie, a Designated Villain can become an Anti-Villain, a Romantic False Lead can become a Dogged Nice Guy... you get the picture. Can often happen when adapting a particularly old work that's subject to Values Dissonance; what makes someone unambiguously evil in one time period can make them more sympathetic in the modern day. Sometimes the writers will even run with this, changing the character to accommodate the performance. If the character dies, expect this version to result in Alas, Poor Villain.
Alternatively, maybe even before or during the performance, a character that was envisioned as unsympathetic may change due to them realising a softer performance works better with the actor or even the desire to incorporate some of the actor's own genuine kindness into their performance.
A subtrope of Actor-Inspired Element, heavily related to Alternate Character Interpretation. Can result in Draco in Leather Pants or Unintentionally Sympathetic if the performance is that effective. In long-running works, remnants of the original persona can sometimes be seen in the earlier parts.
- In an early version of Kung Fu Panda, Po was intended to be something of a Parody Sue, expecting the Furious Five to love him and adore him as much as he liked them. Apparently, Jack Black intervened because he realized how unlikable this made the character, and urged the writers to change Po to being insecure and well aware of his own flaws.
- Frozen had an interesting variant of Music Inspired Heroism, where it was not the main actress who inspired the change, but the performer who sung (and co-wrote) the demo version of a key song. Originally, Elsa was going to be a villain, and the writers "were struggling with how villainous she should be." Then the demo of "Let It Go" was performed by lyricist Kristen Anderson-Lopez, whose vulnerable yet powerful interpretation of the lyrics inspired them to rewrite her as a more sympathetic character.
- A Streetcar Named Desire: An accidental example in the film version. Stanley is meant to be a rotten abusive Jerkass, but Marlon Brando (who had played the role on the stage) imbued him with a lot of sincere emotion (particularly how he bursts into tears when Stella runs out after he hits her). As a result, fans ignored some of his worse qualities and gave him the Draco in Leather Pants treatment.
- East of Eden: Due to a combination of Kate's worse deeds being cut out (the film only adapts the last third of the book) and Jo Van Fleet's performance, Kate seems like a far more sympathetic, tragic figure in contrast to the "born without a conscience" villain she was in the book. It's strongly hinted that she regrets leaving her two sons, and she shares a couple of nice moments with Cal.
- Gremlins 2: The New Batch: Daniel Clamp was intended to be an antagonist, but John Glover's upbeat performance led the creators to retool the character into a more likeable Clueless Boss.
- Jurassic Park (1993): In the source material, John Hammond was a Manipulative Bastard who wanted to keep the park open and making money without any concern for the blatant risks. When Richard Attenborough was cast as Hammond for the film, Steven Spielberg decided to rewrite the character into a more sincere and grandfatherly Author Avatar.
- Kramer vs. Kramer: Meryl Streep found Joanna to be almost unrealistically evil in the initial script. She pushed for the more sympathetic take used in the eventual film.
- The Maze Runner: While the film still presents Gally as an antagonist, Will Poulter's performance clearly indicates that his actions are committed out of genuine concern for the others' safety. As his result, his death scene is treated in a more tragic and sympathetic light and he later turns up alive with a HeelFace Turn in the third film.
- The Mosquito Coast: In the novel, Allie Fox is paranoid, abusive, and slowly goes mad, taking his family along with the ride. In the film, he's played by Harrison Ford, so even in his darkest moments, he's never as menacing or as terrifying as he is in the novel.
- Of Human Bondage: Mildred is a Manipulative Bitch who makes Philip's life hell. Thanks to Bette Davis's performance in the 1934 adaptation, some of the time one gets the impression that Mildred could have loved Philip in her own twisted way. She says the line "you're the only one who ever treated me like a human" in a way that sounds quite sincere.
- Sunshine Cleaning: The original script had Norah as much less sympathetic than she is in the final film - and in many scenes, she is said to be someone who refuses to take responsibility for her wrongdoings. Emily Blunt softens her greatly through her performance, showing that Norah is very much a lost girl who needs direction in life. As a result, some scenes were changed around to reflect this.
- Alan Ladd's wife and long-time agent, Sue Carol, had script approval of The Black Knight and objected to a scene where her husband's character stole a horse. During a script conference she repeated "Alan Ladd does not steal a horse, period. I'm telling you. He steals a horse, we lose the Boy Scouts Association and the Daughters of the American Revolution, to say nothing of his fan club." Irving Allen was equal to the occasion and replied "He's not stealing a horse, Sue, he's borrowing a horse. You know like a Hertz car." "So, show me the difference" said Mrs Ladd, "You keep the stolen horse in and you start looking for another star because we're gonna be on the next plane home." "How would it be" I said, "if we kept all the action up to the point where Mr Ladd disposes single-handedly of the attacking Vikings, then he runs to a sentry and says "Is that the horse I ordered?" The sentry nods in agreement and Mr Ladd jumps on the horse and rides over the drawbridge?" "Yeah, I'll buy that" said Mrs Ladd and that is what was shot. She also instructed Forbes when writing dialogue for Ladd to "keep him monosyllabic".
- Buffy the Vampire Slayer:
- Angel was originally supposed to make a FaceHeel Turn and never turn back. However, David Boreanaz and Sarah Michelle Gellar had become close friends, and Gellar allegedly hated the idea that Angel would not get a chance at redemption, so his character arc was changed.
- Spike was originally meant to be a short-lived villain, but James Marsters proved to be very charismatic, and thus the executives made him a recurring character. This allegedly led to Hostility on the Set, as Joss Whedon, having already soured on "heroic" vampires after being forced to make Angel redeemable, resented having to do it again for Spike.
- The writers conceived Joey as far more of a jerkish lech, which he appears as in the pilot episode. However, they quickly admitted that Matt Le Blanc gave Joey heart and he was turned into a lovable doofus who was more of a charmer.
- Monica's Team Mom quality came entirely from Courteney Cox's characterization - which resulted in the planned Monica/Joey relationship being changed to Chandler, who Monica was now more suited with.
- Game of Thrones:
- Tyrion's nastier qualities were dropped thanks to Peter Dinklage's charisma and the character's popularity. He becomes more ruthless in the books but the show never adapted that part after Season 4.
- Shae likewise was changed from a scheming whore who was Only in It for the Money to someone who genuinely loved Tyrion, and became protective of Sansa — because Sibel Kekilli had a much more sympathetic edge to her. George R. R. Martin even commented that he wouldn't have killed Shae off if he had met Sibel first.
- Inspector Morse: Despite having previously said he didn't want to play cops again after The Sweeney, John Thaw agreed to take the title role in this series on condition that Morse's Chivalrous Pervert tendencies in the books were dropped for the TV series. As a result they were also considerably played down in the subsequent novels.
- Misfits: Simon was originally intended to become a villain, becoming increasingly dark throughout season one and finally resulting in him murdering a woman who was a threat to the rest of the group and hiding her body. However, because the actor (Iwan Rheon) was very charismatic and likeable, it was decided to make him more heroic in season two. This decision was made so late it resulted in other characters quietly sidestepping the murder.
- Once Upon a Time:
- Regina is presented as a straight-up Wicked Stepmother in the first season - who gets the occasional Pet the Dog moment with Henry. Lana Parrilla pushed for Henry to become a proper Morality Pet for Regina, which led to her HeelFace Turn in the third season.
- Zelena too was one villain presented as irredeemably evil. But Rebecca Mader and her geeky adorkable nature - and sheer love of being on the show - led to Zelena eventually getting redeemed too.
- Penny Dreadful: Sir Malcolm Murray was initially created with the intention of being the darkest of the cast (who are all anti-heroes), thus whilst still complicated and even at times sympathetic, season one clearly presents him as a selfish, hypocritical, ruthless and at times flat-out abusive man with a long dark past of bloodshed. It was intended he would mostly carry on this role throughout the entire series run; however, series creator John Logan found Timothy Dalton to be such a friendly and charming person to work with, he decided to incorporate some of this into the character. This led to Sir Malcolm spending a large portion of season two under a spell that made him kinder and more optimistic, and Season three to involve him genuinely developing into a much softer and more heroic individual.
- Runaways: Victor Stein is given slightly more sympathetic character traits than his comic-book counterpart because the writers felt they couldn't justify hiring a seasoned actor like James Marsters to play a one-dimensional child-abuser.
- Saved by the Bell: AC Slater was conceived as Zack's romantic rival, and the early episodes reflect this. But producers found Mario Lopez so nice on set, and his growing friendship with Mark-Paul Gosselaar produced great chemistry on screen. So they wrote Zack and Slater to become good friends, and Slater developed his own love story with Jessie - separate from Zack and Kelly.
- Spartacus: Blood and Sand: Varo was meant to be a Mauve Shirt who died early on. Jai Courtney's friendship with Andy Whitfield led to him being expanded into Spartacus's closest friend and his eventual death became an even bigger Tear Jerker.
- Stranger Things:
- Steve Harrington was originally envisioned as a stereotypical eighties Jerk Jock and Romantic False Lead for Nancy who would die at the end of the season. However, the creators found Joe Keery to be so likable and charming, the character was rewritten as a more complicated individual, with his initial jerkish actions in the show are the result of Toxic Friend Influence and insecurity. This led to Steve gaining a major Heel Realization towards the end of the season, developing into a more decent individual (as well as Nancy not actually breaking up with him until the next season when it's solely down to personal differences). He likewise went through a lot of Character Development during seasons two and three, causing him to develop into a big brother figure towards the kids and become both one of the show's heroes and an Ensemble Dark Horse.
- Billy Hargrove was initially created to act as a replacement jerk for Steve, only much more violent and cruel. His role being the minor but more relatable human antagonist of the season. However, Dacre Montgomery convinced the writers to explore what made Billy that way. This developed into giving Billy a horrifically abusive father, and a tragic past of being taken away from his loving mother at a young age. Leading to Billy spending most of season three as the victim of the Mind Flayer, gaining him some sympathy and even him getting a genuinely heroic death of holding the thing back from killing El.
- On Legends of Tomorrow, Hank Heywood was meant to be one of the main antagonists of Season 4. However, the writers found his actor Tom F. Wilson so charming and likable, they felt compelled to change his character to being more foolishly misguided than outright villainous.
- Supernatural: Castiel was supposed to remain a morally ambiguous angel guide for only a few episodes and then killed off in favor of a more sympathetic angel. However, a positive fan response to Misha Collins's performance led to Castiel having a gradual HeelFace Turn and becoming one of the show's main heroes.
- The Netflix adaptation of A Series of Unfortunate Events features Neil Patrick Harris as the villain, Count Olaf. While the book's character is more terrifying and ruthless, Harris emphasizes Olaf's bumbling nature and makes him more sympathetic. This is hardly a surprise, considering the charisma and likability that Harris brings to every one of his roles.
- Romeo and Juliet: Paris can become this depending on the production. He's there to be an obstacle preventing Romeo and Juliet from being together since he's the one she's betrothed to. As he doesn't do anything outright villainous in the story, he can be portrayed as another innocent victim of the feud alongside the two lovers if the actor says his lines differently.
- King Lear: Edmund is said to be inherently evil because he's an illegitimate child. As he does get a brief bit of redemption towards the end, it's very easy to turn him into a full-blown Anti-Villain without changing the text.
- Les Misérables: Eponine is seen as sympathetic by a modern audience, and some performances of the musical can file off a couple of her more unlikeable qualities (bullying Cosette as a child for instance). Depending on the actress, her hiding Marius's letter to Cosette can either be a scheming bit of Relationship Sabotage or a heat-of-the-moment act of despair.
- Justice League Unlimited: The writers initially wanted Vixen/Mari McCabe to be a very temporary Romantic False Lead for Green Lantern/John Stewart. She was supposed to reveal herself as a big enough jerk that John could break up with her guilt-free and get back with his first love interest, Hawkgirl/Shayera Hol. But Mari's VA, Gina Torres, played her with enough humanity that the writers couldn't bring themselves to make her a jerk. As a result, the writers couldn't come up with another in-character reason for John to break up with her — so their relationship lasted through the end of the series (with some ambiguous clues that John might get back together with Shayera sometime in the future).