Say you have an Evil Twin. Pretty bad, huh? There's always the possibility he might attempt to pull a Twin Switch and blame you for god knows what villainy and force you to go tell your teammates "Clear My Name".
But sometimes, that's gladly out of the question. Back when he was just The Rival you two used to look a lot alike, but since he had his FaceHeel Turn and you both went Cain and Abel on each other, he changed his physical appearance and now people just wouldn't be able to confuse you both. This is symbolic for how two people that would normally be pretty much the same have gone in vastly different ways in life and it shows. Also can represent how the twins have officially stopped thinking like each other.
If this occurs with a pair of opposite-sex Half-Identical Twins, it's likely to occur around puberty, where the development of secondary sexual characteristics makes it a natural time for the two to begin looking different. In real life, even same-sex twins will exhibit this trope as they approach their teen years and grow out of the cute dressing-alike stage, and will go to any lengths to not look exactly alike. Don't be surprised if one twin develops a punk, goth, gender-bending, or some other "wild" look while the other one remains straight-laced.
- In D.Gray-Man, Mana and Nea were nearly identical as kids, the only thing setting them apart being that Mana has slightly longer hair. More than a decade later, Mana is a very tall man while Nea is of average height. Mana has very long hair while Nea has short hair. Oh And they are going full Cain and Abel on each other with the position of Millennium Earl at stake.
- In Trigun, Vash and Knives began this process, doubling as Foreshadowing of Knives' eventual FaceHeel Turn (like we needed it) was when he cut his hair in a different style from Vash's when they were about a year old, in a dramatic scene in a dark room. And said, "if we stay the same we'll have no individuality."
- The cause and the consequence are switched around in Higurashi: When They Cry, were Shion started to resent Mion when she received the tattoo that branded her as the leader of the Sonozaki house. Especially painful seeing how it was meant for her, but they had performed a Twin Switch before the ceremony.
- One story in ×××HOLiC features a pair of identical twin sisters, one of whom suffers from a crippling lack of confidence, especially when comparing herself to her much more vivacious sister. After Yuuko helps her overcome her issues, her price is the girl's long hair. The girl happily complies, saying that her new look is another step towards removing herself from her sister's shadow and pursuing her own personality.
- Inverted in Eyeshield 21: Throughout the entire series, the Kongo twins were nothing alike and didn't seem very close. Not only were they opposites in personality, but Agon had a long mane of dreads. Towards then end of the series Agon's head is shaved bald and he purposely shows it off as a sign of camaraderie towards his brother.
- Part of what impulses the plot of Mint na Bokura: Noel has been so accustomed to be with his twin sister Maria that he simply can't deal with her changing schools for the shallow reason of following a crush, so he follows her to her new school. He doesn't even care that he has to crossdress to stay there, he will get his sis back. Maria, on the other side, while she was genuinely chasing her crush, also was wanting to have a life apart from her brother and is absolutely not pleased with the situation.
- The Quintessential Quintuplets: The titular Nakano quintuplets started doing this around the time their mother Rena died. Yotsuba (the fourth one) was the first to actively attempt it, beginning with wearing a ribbon on her hair to distinguish herself from her sisters.
- Judge Dredd: Joe Dredd and Rico Dredd were clone-brothers, and thus theoretically looked identical at first (Joe being The Faceless.) But by the time we actually meet Rico, he's undergone massive facial cyborging to survive his prison sentence on Titan.
- Played with in Yoko Tsuno. Khany and Poky were young twins when they were placed into suspended animation. They were awoken at different dates, resulting Khany being an adult and Poky remaining a child.
- Jean-Paul and Jeanne-Marie Baubier—aka Northstar and Aurora of Alpha Flight—started off as Half-Identical Twins with complimentary outfits and powers, but after the two had a falling out, Jeanne-Marie changed her costume to be different and altered her powers using her boyfriend Sasquatch, a geneticist, so they weren't reliant on touching each other. The twins have since made up, but maintain their separate costumes.
- In Karma in Retrograde, Touya suffers this with his twin, Fuyumi. From his perspective, he's jumped forward five years in time, during which the twin sister he used to dote on has grown up and become a kindergarten teacher while he still has the mentality of a high school student.
- Army of Darkness: Evil Ash gradually becomes a monstrous Undead due to all the damage he receives from his twin.
- Captain Picard and Praetor Shinzon in Star Trek: Nemesis are like this. As a clone created more recently, and suffering from an illness that causes (awesome-looking) Glamour Failure, and having been injured and improperly healed several times, Shinzon looks very little like Picard does, and probably wouldn't be an exact match for Picard at 20note . The idea of impersonation, etc. never comes up. A villain who wasn't a clone of Picard could've worked nearly as well - except for the part where he needs Picard alive in order to cure himself, and what he represents - had his life gone differently, Picard could perhaps have been just as evil For Want of a Nail. Picard tells him that the reverse is true, and that Shinzon has equal potential for good. (Shinzon stays a bad guy anyway, though.)
- House of Wax (2005) has twins Nick and Carly as the protagonists. Nick was often in trouble as a child, and their parents would often compare him unfavorably to his sister. This resulted in a Then Let Me Be Evil situation - as he went out of his way to be a delinquent while Carly was the responsible twin.
- In the Robert A. Heinlein's Time for the Stars, after the more easygoing twin discovers his more dominant brother manipulated him into going on the interstellar voyage in his place. (Relativity plays a hand in it as well.)
- Caramon and Raistlin Majere from the Dragonlance books. To be honest, they were pretty different when the story started, but not so much before a certain traumatic event. Caramon has always been bigger and stronger, though. Also, during the story, their differences grow even more.
- Occasionally, though, they happened to have a very similar facial expression. In those cases, there was always a third party character pointing out how much they look like and how foolish he/she was, not having seen that earlier.
- In a mild version of this trope, when Lori returns to Finch with Bree Pym near the end of Aunt Dimity Down Under, Ruth and Louise Pym ask to see both of them. After the introductions, Ruth and Louise turn to Lori and drop their lifetime ping-pong speech habit to each thank Lori individually.
- Vorkosigan Saga has Mark Pierre Vorkosigan. His was created to mimic Miles Vorkosigan by a Barrayaran enemy, but since Miles' deformities are a result of cell damage in the womb Mark develops normally, and requires surgeries (including forces bone replacement) to mimic his clone. When he gets out from under his handler's thumb his first reaction is to gain an enormous amount of weight to help distinguish himself, as well as counseling to help define his identity.
- Cersei and Jaime in A Song of Ice and Fire. Together, they form an unstoppable scheming machine enough to rival their father. But they really start to change once they are separated for a long time and endure horrible traumas to which they respond in entirely different ways — Jaime pulling a HeelFace Turn and Cersei a Villainous Breakdown. And even when reunited, they each start to loathe the person they see their twin is becoming.
- In Jacqueline Wilson's Double Act, Ruby chops off all her hair to symbolise that she wants to be more independent from her sister Garnet.
- Justified in The Vampire Chronicles, where the red-headed, green-eyed twins Maharet and Mekare have been separated for thousands of years, having been placed in coffins and dropped in different oceans. Maharet had her eyes poked out, and Mekare's tongue was cut off for leading a rebellion against the vampire Queen Akasha and her King Enkil. Maharet spent the millennia caring for the progeny of her human daughter. Mekare eventually shows up at the end of the 20th century as a crazy savage incapable of communication. After Mekare kills Akasha and eats her brain and heart, she absorbs the spirit of the blood spirit Amel into her body and becomes the new Queen of the Damned. Despite this, she never regains her sanity, and Maharet keeps her secluded from the world.
- A short-term version was used in one of Isaac Asimov's Union Club mysteries. A thief with an accomplice who closely resembled him (providing hard-to-crack alibis) had a job go sour to the point where he shot the store owner and fled. The best plan he could come up with on the fly was to quickly rendezvous with his "twin" so that it would be difficult to conclusively prove which of them was the culprit. They were both wearing glasses with built-in antiglare — the thief had been outdoors in the sun, so his glasses were dark; the accomplice had been indoors, so his were clear.
- Chronicles of the Kencyrath: When they were children (birth to age 7) Jame and Tori were very close. They were almost indistinguishable as prepubescent Half-Identical Twins. They crossed easily and comfortably in each other's dreams. And then they were separated when they were 7. By the time of the books, they're a world apart—they've lived incredibly different lives, are 10 years apart in age, and torn apart by a huge amount of emotional baggage. But now, the trope is being Inverted: After being reunited, they're slowly starting to synch up again.
- Dante and Vergil had a heated rivalry in Devil May Cry 3 but still felt somewhat guilty about it. That game was a prequel to its predecessor, Devil May Cry, where they really stopped pulling the punches and Vergil is now the hulking Tin Tyrant Nelo Angelo, although Dante didn't know it was Vergil under the armor until after the final battle. The player might have guessed, what with the hints and all.
- In Metal Gear, Liquid Snake went from just another megalomaniac with a nuclear tank to Snake's Arch-Enemy once he performed a Grand Theft Me on The Dragon, Ocelot. Subverted because he really is dead and the whole possession thing was just a bluff by the end.
- Also, they started out life looking identical (both being clones of Big Boss) and received near-identical upbringings (one in the US military, one in the British). However, sometime after they split up as children, Liquid became a megalomaniac, had his hair bleached blonde due to his time spend as an Iraqi POW, grew it out, and stopped wearing a shirt. Solid sticks with the "brown mullet, spysuit, and professional terrorist and conspiracist fighter" motif daddy used back when he was a Snake.
- In Mother 3, this is subverted as people still mistake Lucas for the Masked Man, even though one wears a large cybernetic helmet at all times..
- Warcraft: Malfurion and Illidan Stormrage. Though they weren't identical twins to begin with (they had at least different hair colors), Illidan lost his eyes and got glowing tattoos with his first Deal with the Devil, and bat wings, horns and furred legs with hooved feet when he absorbed the power of an evil artifact. Malfurion looked like a relatively normal night elf for a while (with the exception of stag antlers), but he has now gained other animal traits, like bear paws and bird wings.
- The War of the Ancients trilogy reveals that they had different personalities to begin with. Malfurion wanted to learn the ways of Cenarius to become a druid and take care of nature. Illidan initially exhibited interest in learning the druidic ways but got impatient and took the easier road of learning sorcery instead. Both brothers had feelings for Tyrande, though.
- Porom in Final Fantasy IV: The After Years now has a Stripperific outfit and pink hair, while her brother Palom who, despite an age up from a child to a teenager, doesn't look much different from how he looked in the original game. They had a very heated discussion after Palom decided to move from their village and become a sage like Tellah.
- Edgar and Sabin from Final Fantasy VI used to look exactly the same when younger. Then, the faithful coin toss happened and Sabin left the castle while Edgar stayed behind and became king, bringing them to grow up in two completely different environment. Ten years later, after living separate and opposite lives apart from each other, Edgar is now a young man with elaborate clothes fitting a king, waist-length hair tied by two ribbons and an average build, while Sabin is taller than his brother and way more muscular, wears a plain monk outfit, has shoulder-length hair in a simple and practical ponytail and a beard.
- Basch and Gabranth from Final Fantasy XII have this going on now, but Gabranth actually did impersonate Basch years ago to frame him as a traitor. They can easily be told apart as Basch has long hair and beard while wearing simple clothes, plus a nasty scar courtesy of Gabranth during the impersonation scheme. Gabranth or Noah technically has short hair, a small goatee and is clad in armour as a judge.
- Star Wars Battlefront: Elite Squadron features two Force-sensitive clone troopers, X1 and X2. X1 goes bald when he turns to the Dark Side.
- The webcomic Melonpool has both Ralph Zinobop and his nice clone Ralphie as main characters. Though physically identical, Steve Troop draws them with such different expressions and body language that it's almost always easy to tell who's who.
- The Inexplicable Adventures of Bob! has Molly the Peanut Butter Monster and her clone Galatea, or "Golly." Though physically identical, their facial expressions, body language, and speech patterns have always been radically different, such that the only people who ever confuse one sister for the other are those who don't know there are two of them. These days it's even easier because Golly has taken to wearing clothing, while Molly still revels in furry nudity.
- The Polar Opposite Twins of Bomango, Didi and Gogo. Didi, the Lipstick Lesbian Mad Scientist, cut her hair short. While Boisterous Bruiser, Gogo, started working out and now has a very muscular physique.
- In Drowtales, fraternal twins Mel and Kel used to look similar enough to pull a Twin Switch at school, but by the time they're adults their physical appearance and philosophies have diverged so much this is no longer possible, and it culminates in Mel assassinating her brother in cold blood.
- Parodied on Futurama: The Professor's clone doesn't look like him because he was kept in a test tube too long and his face was mashed against the glass. Not that anyone would make the mistake of confusing the two in the first place, as there's an approximate age difference of 148 years between them.
- Totally Spies!: Jerry's brother, Terry, went through plastic surgery to make himself absolutely incomparable to Jerry. This is all for placing the blame on him for cheating and making him repeat the Second grade
- In Rugrats, the twins each decided to act more like someone else so their parents could tell them apart easier. Lil chose Angelica and put her hair in pigtails while Phil chose Chuckie and messed his hair up.
- In Kong: King of the Apes, the show's Minor Kidroduction had Lukas and Richard looking pretty much identical, except for clothes; the other signs were minor, like Lukas having freckles in close-up shots. The flashback ends with Richard getting a bionic eye after an accident, which ties into his Start of Darkness.
"I'm glad I look different. I hated being a twin."
- A Truth in Television semi-example would be Benji and Joel Madden of the band Good Charlotte. While not a matter of good and evil, they are identical twins who go out of their way to look nothing alike.
- Brie and Nikki of the Bella Twins originally went out of their way to look identical (Nikki even doing daily workouts to match her sister's smaller frame). But once the show Total Divas started airing, establishing how they really were Polar Opposite Twins, Nikki began differentiating herself from Brie by getting breast implants, developing Amazonian Beauty physique as a result of weight training and adding blonde streaks to her hair. They've virtually abandoned keeping themselves identical by now.
- Max and Charlie Carver made a name for themselves playing identical twins on Desperate Housewives and Teen Wolf. But after their stint on Teen Wolf, they began taking more roles separately. Charlie in particular came out as gay in 2016 and started appearing in Queer Media, carving out a definite niche for himself separate from his brother.