A pair of performers fall in love while working together, possibly even getting married and/or having kids over time. This happens quite a bit in Hollywood and is prime tabloid fodder. Such relationships seem to have a high breakup rate, but there are some long-lasting marriages that started this way.
What is actually being filmed is largely irrelevant. They're often a couple onscreen as well—when you spend all day pretending to be in love with someone, you may end up Becoming the Mask. However, it doesn't always happen that way. The point of the trope is that behind the scenes the two fall for each other.
The Muse is a Sub-Trope, which is about a male movie director falling in love with his lead actress. Cast Incest is another subtrope, namely the first type where the couple met while playing relatives, which adds a level of Squick before further thought reveals that it's no different from any other role.
In live theatre circles, the phenomenon is known as a "showmance" and tends to annoy their costars to no end. When it happens within a musical group, it's known as "bandcest," and while it tends to end badly, the fallout from the breakup often leads to the band's most famous work. Just ask Fleetwood Mac.
- Model Kate Upton and pitcher Justin Verlander began to date after meeting on the set of a commercial for the Major League Baseball 2K12 video game. They eventually married in late 2017, fittingly after Verlander helped the Astros win the World Series that year.
- Kenichi Suzumura and Maaya Sakamoto were first acquainted with each other when working on Mizuiro Jidai in 1996. In 2004, they were cast together as Shinn Asuka and Lunamaria Hawke, respectively, in Mobile Suit Gundam SEED Destiny. As the years went by, they seemed to constantly play love interests in a lot of titles they were cast in together, such as Zack Fair and Aerith Gainsborough, Mikiya and Shiki, and in a more one-sided case, Hikaru and Haruhi. Then in 2011, they got married.
- This happened between American voice actors Monica Rial and Matt Kelly while they were doing voice acting in Blue Seed. Monica was Momji and Matt was Kusanagi. They married after the voice dubbing was done. But they divorced shortly afterwards.
- A-list stars Yūki Kaji and Ayana Taketatsu shocked the entire anime world when they announced their marriage all of a sudden in June 2019. Seiyuu fans are rife with speculation on when exactly their relationship started since the couple kept it under wraps extremely well (the first anime they both were cast in was Star Driver from 2010), but a good number of watchers are pretty sure that High School Dx D must have played a role in it. Extra points for having Issei and Koneko as love interests (one of many for Issei) and the anime adaptation ongoing in one form or another from 2012-2018, as well as other DxD adaptations with voice acting such as video games, radio shows, and drama CDs.
- In-Universe example in Yuri Is My Job. Nene Saionji and Yoko Goeida entered into an actual romantic relationship while working at the Liebe Girls' Academy salon, in which they roleplayed as students at an all-girls school. This was on top of their relationship as "schwestern," which they formed by Saionji dissolving her own schwestership with Sumika. The relationship ended very badly, with Goeida leaving Saionji behind without batting an eye, and Saionji being hurt so badly that she left the salon for good... but actually stayed on as a cook.
- Takuma Terashima married Satomi Sato in 2017. Their best-known project cast together is The Irregular at Magic High School as Leohart Saijo and Mizuki Shibata, although it should be noted that their relationship had already started in 2009, five years before that anime debuted in 2014.
- On December 29, 2019, Tasuku Hatanaka and Sayaka Senbongi announced they had gotten married. When it comes to seiyuu relationships, this one went at lightning speed compared to most other marriages in the business: The two had first met when they were cast together as the main characters of Kabaneri of the Iron Fortress only a little over three and a half years earlier. As a bonus, said characters also develop romantic feelings for each other.
- Kazuhiro Yamaji and Romi Park posted their marriage announcement on January 22, 2020 (which was Park's 48th birthday). Both of them are veteran voice actors with decades of experience in the industry, but their one major project together was in Attack on Titan's third season, voicing Kenny and Hange.
- Tomoaki Maeno and Mikako Komatsu announced their marriage on May 12, 2020. They've been in a few anime together, such as Yu-Gi-Oh! ZEXAL's second season, Pretty Rhythm Rainbow Live, and Fairy Gone, always where one plays a major character while the other is a minor supporting character. However, their most significant shared voice acting project was when they played the two lead characters of Aoharu × Machinegun, to the point that the creator of the manga even made a special drawing of their characters in honor of their marriage.
- Shinji and Asuka in the Advice and Trust Animated Actor omakes are just as in love with each other as their In-Universe counterparts (but without any of the codependency issues). Later omakes reveal that they got married in secret during a trip to Vegas.
- Happens In-Universe between Phineas and Isabella in Finding Dad while they sing a karaoke duet version of their one hit wonder Gitchee Gitchee Goo before having their first kiss.
- The Norwegian voice actors of Nani and David from Lilo & Stitch, Heidi Gjermundsen Broch and Nicolai Cleve Broch would later get married in real life. They would also later do the voices of Riley's parents in the Norwegian dub of Inside Out.
- Sleeping Beauty: Mary Costa, the voice of Aurora, revealed in an interview that during production, she and the actresses playing the fairy godmothers (Verna Felton, Barbara Jo Allen, and Barbara Luddy) were all attracted to Bill Shirley, the voice of Prince Phillip, and flirted with him.
- In the short story "Who Am I This Time?" by Kurt Vonnegut, the main character completely takes on the persona of whatever character he performs in the community play. A beautiful but socially awkward woman, when performing A Streetcar Named Desire with him, falls in passionate love with his persona. By living a life of Romance on the Set through various plays, they become Happily Married.
- In-Universe in Redshirts, Jenkins, whose wife had been Redshirted years before, sends a love letter to the actress who played her in Chronicles of the Intrepid when Dahl and the others go to the real world. In one of the epilogues, it is implied that she then ends up in a relationship with the actor who played him.
- In the commentary for The Tales of Beedle the Bard, Professor Dumbledore mentions the unfortunate casting choices in a theatrical version of the story The Fountain of Fair Fortune - the students playing "Amata" and "Sir Luckless" had been dating until "one hour before the curtain rose," at which point "Sir Luckless" dumped "Amata" for the girl who was playing "Asha." The two actresses began to duel and the resulting disaster is why Hogwarts no longer does school plays.
- At least one couple in We Are All Pokémon Trainers have ended up in a relationship just like their characters.
- French tenor Roberto Alagna and Romanian soprano Angela Gheorghiu are perhaps the most famous couple in the opera world. Having met and fallen in love with each other during a production of La Bohème in Covent Garden in 1994, they married 2 years later. In their 12-year on-off marriage, they have performed together onstage, done concerts and recorded albums together many times. However, in 2013, they've divorced for good, and Alagna has since remarried.
- Italian soprano Mirella Freni married Bulgarian bass Nicolai Ghiaurov after they frequently performed together. Their first performance together was a production of Faust in Genoa in 1961, and they married in 1978.
- American soprano Patricia Racette fell in love with American mezzo-soprano Beth Clayton during a production of La Traviata in Santa Fe in 1997, and they married in 2005. They are currently the most famous lesbian couple in the opera world.
- American tenor Charles Castronovo met Russian soprano Ekaterina Siurina when they performed together in a production of Donizetti's L'elisir d'amore in Berlin in 2004, and they married in 2005. They've frequently performed together at many opera houses since then.
- Spanish soprano Montserrat Caballé married Spanish tenor Bernabé Martí in 1964 after they fell in love during a production of Madame Butterfly in A Coruña.
- African-American soprano Leontyne Price married African-American bass-baritone William Warfield during a European tour of Porgy and Bess, in which they performed together. However, they divorced in 1972.
- Russian soprano Anna Netrebko started a relationship with Yusif Eyvazov, an Azerbaijani tenor, during rehearsals of Puccini's Manon Lescaut in Rome in 2014. A year later, in 2015, the two got married.
- Olga Peretyatko, another Russian soprano, met Italian conductor Michele Mariotti during a performance of Rossini's Sigismondo in Pesaro in 2010, and they married in 2012. However, they divorced in 2018.
- Bulgarian soprano Sonya Yoncheva married Venezuelan conductor Domingo Hindoyan after falling in love with him during an audition for Verdi's La Traviata at the Berlin Staatsoper.
- Romanian soprano Virginia Zeani met Italian-Russian bass singer Nicola Rossi-Lemeni during performances of Bellini's I puritani in Florence of 1952. However, they met again during a production of Handel's Giulio Cesare at La Scala in 1956, and they married a year later.
- Spanish soprano Ainhoa Arteta married American baritone Dwayne Croft after they met a year before during a production of Fedora at the Metropolitan Opera.
- German soprano Diana Damrau met her husband, French bass-baritone Nicolas Testé, in a Munich church while performing Jean Francaix's oratorio L'Apocalypse Selon, and they have been married since 2010.
- Lithuanian soprano Violeta Urmana married Italian tenor Alfredo Nigro after they both met during a performance of Gluck's Iphigénie en Aulide at La Scala in Milan in 2002.
- Latvian mezzo-soprano Elina Garanca married British conductor Karel Mark Chicon after meeting in a concert where he conducted and she sang.
- Italian tenor Fabio Armiliato met Italian soprano Daniela Dessì during a double-production of Mascagni's Cavalleria Rusticana and Leoncavallo's Pagliacci while on a Japan tour with the Met in 1997. Their first official performance together was in 2000, in a production of Giordano's Andrea Chénier, and they married sometime after, and often performed and recorded together.
- French-Canadian baritone Étienne Dupuis and Australian soprano Nicole Car first met during a production of Tchaikovsky's Eugene Onegin with the Deutsche Oper Berlin in 2015. They have married since then, and frequently perform together in productions and concerts.
- French-Canadian mezzo-soprano Huguette Tourangeau met Barry Thompson, director of the Edmonton Opera Association, while she was performing in Verdi's Rigoletto in Vancouver, and they married in 1969.
- American tenor Bryan Hymel first met Irini Kyriakidou, a Greek soprano, on the set of Bizet's Carmen at Covent Garden in 2009, and they both married just under a year later.
- Polish soprano Aleksandra Kurzak first met Roberto Alagna (the then-husband of Angela Gheorghiu) during performances of L'elisir d'amore at the Royal Opera House in 2012. Following Alagna's divorce from Gheorghiu, the two started a relationship, and got married in late 2015.
- Japanese songstress LiSA (real name: Risa Oribe) married voice actor and fellow singer Tatsuhisa Suzuki on January 22, 2020. They've had one project together: the video game Sword Art Online: Fatal Bullet, where she sang the opening song "Thrill, Risk, Heartless" while he voiced major character Itsuki.
- In-Universe in Darths & Droids. Annie and Jim, respectively the players of Anakin and Padme, start dating after Episode II. They continue dating in the original trilogy, but change characters to Leia and Han.
- In Twokinds, one of the "Sketch of the Day" pages shows Trace and Laura dating in 'real life', commenting that some fans think he and Flora are together even 'off-screen'.
- There have been several Channel Awesome couples:
- Obscurus Lupa and Phelous, who became engaged in 2021.
- Nash and JesuOtaku, although they eventually broke up.
- Lindsay Ellis (The Nostalgia Chick) and Todd Nathanson (Todd in the Shadows). In-universe, this has been translated to the Chick having an obsessive and completely unrequited interest in him, while he continues stalking Lupa. While they have since broken up, they remain great Amicable Exes and Todd even attended her wedding.
- Paul Schuler and Elisa Hansen (who plays Maven of the Eventide, Dr. Tease and the Makeover Fairy in the Nostalgia Chick's videos) are now married with two children.
- Dominic Smith and Heather "Calluna" McDonald also met and fell in love through their association with the site, though they broke up in early 2020.
- Mary Kate Wiles and Sean Persaud met on the set of Shipwrecked Comedy's series Kissing in the Rain, and later started dating. They've since played Official Couples on almost all of the group's projects.
- The French voices of Homer and Marge in The Simpsons (Veronique Augereau and Philippe Peythieu) got married in 2001.
- The voices of Kif Kroker and Amy Wong in the Latin American dub of Futurama are a married couple.
- Wayne Allwine and Russi Taylor, the voices of Mickey and Minnie Mouse, were Happily Married until Allwine's death.
- Slightly one-sided with Recess: Jason Davis, who played Mikey, had a crush on Ashley Johnson, who played Gretchen, when the show was on. In the show itself, there's no shipping.