A plot device has in some way swapped the roles of several of the characters or has had one character take the role of another and that one has a new role. They've effectively changed destinies with one another.
This often happens in an Alternate Universe setting. This sometimes has a drastic change on the plot as the characters will often maintain their personalities or at least one of them will and this changes how events take place.
This can sometimes lead to the canon main character turning into a supportive character while a once supportive character is now the main character.
It's more common in fan fictions. The author may switch two characters' roles around around and still have the plot play out mostly the same. However, sometimes the author will have the differences in personality as well as other factors make change in how the plot goes.
- In the Naruto movie Road to Ninja, Naruto and Sakura are sent to an alternate world where Naruto's parents are alive while Sakura's are dead. In this world Sakura's parents are heroes and her father was the fourth Hokage, both of them gave their lives protecting the village. Many of the younger kids look up to Sakura for this. Most of the characters in this world have opposite personalities from their counterparts; the two that are role reversed are Kakashi and Gai. The Akatsuki are also good guys in this world.
- One Piece: Pre-Time Skip, the great prison Impel Down is headed by the Chief Warden Magellan, with Hannyabal the Vice Warden at his side. Post-Timeskip, Hannyabal now becomes the Chief Warden while Magellan is demoted to Vice Warden.
- Puella Magi Madoka Magica: The intended consequences of Homura's wish. Before Homura became a Magical Girl, she was a physically and psychologically weak Shrinking Violet, who was protected by a then-magical girl Madoka. Homura's contract involved her going back in time to redo her meeting with Madoka so that she could be protect her, instead of the other way around. After Madoka asks Homura to prevent Kyubey from tricking her into consenting to the contract, Homura does this, and non-magical girl Madoka ends up with some insecurities, similar to Homura originally, although not to the same extent.
- Legend Of Katara: Has it set that Aang didn't surive his long stasis and died soon after being released after being set free of the iceberg. Happening years early then the show, Katara is born becoming the Avatar. Being the last Airbender the other past lives give him a chance to stay with her as a spirit to help her learn airbending and to guide her. In return he will be given a second chance at life.
- Naruto fanfic Dead Garden. For some reason Minito picked Sakura to be the jinchuuriki for the Nine Tails instead of Naruto, who has chosen to become a Medical Ninja (much sooner than Sakura did) so he can help his mother. In this world Sakura doesn't take the fact that she contains the Nine Tails very well and it affects her already low self-confidence. And Naruto is still pretty much the same.
- Bleach fanfic Getting It Right. After the battle with Aizen Ichigo lost everyone he cared about. Kisuke offers him a chance to keep that from happening by sending him back into an alternate timeline. However instead of him having the massive amount reiatsu it is Orihime that has it and the Ichigo of this timeline died in a hit and run accident the moment he arrived. The day the Original Ichigo met Rukia it is Orihime that Rukia visits and ends up turning into a Shinigami. Orihime still has her cheerily personality. The personality of the Ichigo of this timeline is not entirely known but it appears that he was carefree due to his mother still being alive.
- Torque: Taking place during Jak II: Renegade, Jak is a loyal brainwashed Dark Warrior of Barron Praxis. Keira with the help of Daxter is forced to take on the path that Jak was meant to follow in order to save him. In a sense the story was changed from Jak 2 to Keira and Daxter.
- There are a handful of How to Train Your Dragon fanfictions that do this with Hiccup and Astrid. As well as switching Hiccup with Valka around by having Hiccup being the one taken by dragons.
- The How to Train Your Dragon fanfic Souls of Dragons features Astrid as the one who was taken away by dragons at the age of three and Valka still living on Berk. The events of the story take place over the second movie. The events of the first movie did take place by the author says in the place of Astrid is Hiccup's sister. Being taken at the age of three and with limited human interaction since Astrid is far more feral then Valka was in the second movie. Many human interactions she regards with confusing or as threating. She also doesn't understand sarcasm, briefly misinterpreting it as lying. The story plays out differently then the second movie but with some key story points taking place. it also has a bit of "magic" in it. Astrid isn't to found of Hiccup in the beginning.
- There exist two My Little Pony: Friendship Is Magic fanfictions in which Twilight Sparkle and her Gender Flipped counterpart Dusk Shine change roles. One of the fics shows the events from Dusk's perspective and the other shows them from Twilight's perspective.
- Fairy Tail fanfic Alternate Tail Series uses this as the main premise, with the primary team consisting of Gajeel (switching with Natsu), Lyon (Gray), Mirajane (Erza), Levy (Lucy), and Pantherlily (Happy).
- Danganronpa fanfic 'and back to despair again' switches the cast of Danganronpa 1 and 2, but doesn't go with a direct character-to-character switch. Nekomaru Nida is the protagonist of the Killing School Life, Mondo Oowada is the protagonist of the Killing School Trip, Aoi Asahina was the Future Foundation spy, and Peko Pekoyama is the original Mastermind.
- Tengen Toppa Gurren Lagann fanfiction Tengen Toppa Gurren Solvernia switches the role of Nia and Simon, with Nia being the young orphan who follows Kamina to the surface with her Gunman Solvernia, while Simon is the discarded son of Lordgenome.
- Star Trek (2009)
- For a time Spock is the Captain of the Enterprise and Kirk is the First Officer.
- In the sequel the famous death scene from Star Trek II: The Wrath of Khan is swapped around so that it is Kirk that dies instead of Spock
- In Back to the Future Part III, Marty and Doc's roles of "voice of reason" and "swayed by emotions" are reversed, so much so that at one point they even exchange their respective "Great Scott!" and "This is heavy!" catchphrases.
- In the fourth book of A Series of Unfortunate Events, Violet, the invention-oriented sibling, has to do a ton of overnight research while her more literary-minded brother is away at the doctor. Later on at the climax Klaus has to briefly take her role as the inventor and quickly make a device that will save their friend from being sawed in half.
- At the start of the Power of Three arc in Warrior Cats, Jaypaw is determined to become a warrior, while Hollypaw wants to be an important member of the Clan and starts training as a medicine cat. Partway through the book, Jaypaw accepts that his blindness is too much of a disability to hunt or fight and that he has a special connection with StarClan, while Hollypaw struggles with healing and realizes that she longs to be a warrior, so they end up being allowed to swap roles.
- One episode of M*A*S*H had the 4077 celebrating Boxing Day to make a group of British patients feel more at home, which resulted in Klinger switching jobs with the Commanding Officer for a day.
- In the Space Cases episode "Both Sides Now", Davenport suddenly gains psychic powers that enable her to swap the kids' races and personalities (so that Radu becomes human, Harlan becomes Andomedan, etc.) This also forces the kids to swap roles aboard the ship.
- In the Seinfeld episode "The Opposite" George decides that everything he's done in his life is wrong, so he's going to do the opposite of whatever his inclination is. He suddenly becomes very successful including landing his dream job with the Yankees. Meanwhile, Elaine suffers a series of setbacks which lead to the company she works at going out of buisiness.
Elaine: Do you know what's going on here? Can't you see what's happened? I've become George.Jerry: Don't say that.Elaine: It's true. I'm George! I'm George!
- In another episode Kramer and Jerry swap apartments and end up acting like each other.
- Person of Interest: When Reese is shot, Finch is forced to do all the field work while Reese sits behind the computer.
- Smallville: As Clark and Lois start getting serious about their relationship, Jor-El decides Lois needs to really understand Clark if she's going to spend the rest of her life with him. So Jor-El takes away Clark's powers and gives them to Lois for a day. Hilarity Ensues.
- In the Stargate SG-1 episode There But for the Grace of God Jackson arrives on an Alternate Universe Earth, one of the key differences is that O'Neill and Hammond have switched ranks.
- On an episode of Welcome Back, Kotter, Kotter and the vice-principal Mr. Woodman change jobs, leading to Kotter becoming the grumpy martinet no one likes and Mr. Woodman the cool teacher (who even dresses up as George Washington for a history lesson at one point).
- The Book of Mormon: At the beginning of the play, Elder Price is the missionary that everyone believes is going to be most successful and Elder Cunningham is his sidekick. By the end of the play their roles have reversed; Elder Cunningham becomes the most successful evangelist (of his own religion) and Elder Price is just one of his assistants.
- Briefly done in Batman: Arkham Asylum during the last encounter with Scarecrow where the intro of the game is played again but with Batman and the Joker switched around.
- The Ensemble Stars! story Mismatched Pair Lessons has a minor version of this, as it revolves around Anzu encouraging the characters to learn from one another and try new things by having them exchange units temporarily. Shinobu and Yuuta, Wataru and Keito, Tori and Hajime, and Kanata and Souma all swap outfits and try acting as a member of the other's unit for an afternoon.
- Kim Possible
- In episode "Bad Boy" Ron is turned evil and Drakken is turned good by the Attitudinator. Ron gains Drakken's blue skin while Drakken gains white skin. Ron turns out to be a very threatening villain compared to the other evil doers and unlike Drakken can keep Shego in line. And almost beats Kim.
- Ron is momentary turned evil again in "Stop Team Go" much to Shego's horror.
- In the Penn Zero: Part-Time Hero episode "Totally Into Your Body", Penn and Boone accidentally switch positions as they are being transported, leading them to switch roles in a "Fantastic Voyage" Plot. Now Penn is the patient rather than Boone, while the woefully unprepared Boone has to play the hero role.
- In Phineas and Ferb, Candace and Vanessa have their roles in the show switched after an accidental Clothing Switch.
- In Ben 10 there is an episode in which Ben unexplainedly winds up back in the pilot, but Gwen ends up with the Omnitrix instead of him.