Temporary Love Interest

In an arc-less show, one in which each episode stands alone, the hero cannot be allowed to have long-running relationships. A girl/boy friend would interfere with opportunities to insert romantic tension.

Thus, the Temporary Love Interest who shows up has a brief idyllic relationship with the hero, then dies tragically. After that, she's usually never mentioned again. If she's put out of the picture without dying, she's a Girl of the Week. If a character has loads and loads of Temporary Love Interests, they may have a Cartwright Curse.

Related to Romantic False Lead, except that relationship must die for the Official Couple to be able to get together.

Anime and Manga

 * RahXephon gives a particularly dramatic send-off, but it comes down to the same thing.
 * Most of the secondary male characters in Sailor Moon who get close to the girls only appear in one episode; in fact, most of the familar supporting cast was, over time, completely phased out. The major exception was Yuuichiro, the slacker who lived at Rei's temple for several seasons. Ami's popularity with the fandom let her ambiguous rival/love interest relationship with the boy Ryo come up just twice.
 * Kirby of the Stars: Whispy, of all people, who is a talking tree gets his Temporary Love Interest in the form of a flower. Dedede has her transformed into a monster, and Kirby has to kill her. To make things even more bizarre, when Whispy fell for her, she wasn't even sentient. She didn't come to life until after the transformation started.
 * Four Murasame from Zeta Gundam.
 * Stella Loussier from Gundam Seed Destiny.

Comics

 * When the kids from Runaways went back in time to 1907, Victor found himself falling in love with a girl named Lillie. Their relationship followed this trope to the letter, except that she didn't die; she just decided at the last minute that she couldn't go with him back to the present.

Film

 * Austin Powers (all of them).
 * Which in itself parodies the same concept from James Bond.
 * Even when James Bond has a love interest that actually manages to survive the entire movie, she's almost invariably completely forgotten in the next movie.
 * Parodied in a Robot Chicken sketch which shows that he turns into a clingy wimp (and a selfish lover) whenever he actually gets the girl. The reason he's always single again for the next film is that each of the girls dumps his ass when they realize how lame he is.
 * The Big Country

Literature

 * In the Star Wars Expanded Universe, Luke Skywalker went through girlfriends like most people go through socks. It was so sad. Fortunately, the suffering ended when he married Mara Jade.
 * The Mortal Engines quartet has two of these: ; in an interesting variation, also has a Temporary Love Interest

Live Action TV

 * Stargate SG-1: Carter is a total black widow, and Daniel Jackson hasn't done too well either; nearing the end of the series, Carter just got a seemingly-long-term boyfriend that still made an extended stay in the hospital during his introductory episode, and the height of Daniel Jackson's success is a love interest that merely spent a couple of seasons possessed (and effectively dead). The SG-1 team, like so many other heroes, may be effectively bulletproof, but best not to get involved with them: it does not rub off. Dr Jackson eventually averted this by hooking up with a fellow member of SG-1 in the finale...only to have the relationship fall victim to a (literal) Reset Button.
 * These happen in Atlantis too: Sheppard and very rarely McKay are on the receiving end. While, to some people, Sheppard had tons of UST going on with Weir, her disappearance mid-series left him without a single potential relationship that would last beyond a single episode. McKay on the other hand took his time and ended up with in the final season.
 * Early seasons of The X-Files did this with Scully dating random dudes for an episode, Mulder had porn.
 * The early first season episodes of Xena: Warrior Princess were notorious for providing both Xena and Gabrielle with a doomed Temporary Love Interest, including what is perhaps the most extreme example of the form as a whole, Marcus: he actually died twice. No wonder they quickly shifted to Ho Yay.
 * Smallville had two for Clark. The first one died, and the second one was put in prison. However, Shipping was so great they decided to bring her back for two episodes and kill her to stop it. The latest season introduced a third who also died in her second appearance. Of course we know how it'll end up, which makes temps a requirement until the show ends. Lex has also had several, and married a few of them.
 * Happens in an episode of Knight Rider, when Michael Knight's bride is killed before the wedding ceremony ends.
 * Gilina Renaez (The PK Tech Girl) in Farscape's first season. In fairness, she had more than one appearance. It's just that in the second she found out her true love who she was risking her life for had the hots for someone else. Then she died tragically.
 * Supernatural Any girl with Sam or Dean.
 * Any girl who asks the Doctor if she can travel with him on the new season of Doctor Who. In
 * Rose Tyler. In
 * River Song. In . Despite this, we see her past self go on many adventures with the Doctor, his companions, and eventually.
 * The Sarah Jane Adventures gives us Peter Dalton.
 * Averted on Star Trek: Deep Space Nine by Benjamin Sisko's long-term girlfriend Kassidy Yates (although she did get Put on a Bus at one point, by the end of the series she was a fixture in Sisko's life). But played straight with Kira's love interest Bareil.
 * Star Trek: The Original Series has what might quite possibly be the Trope Codifier: Edith Keeler of the truly exceptional episode "The City on the Edge of Forever."
 * In the original Charlie's Angels, any man an Angel shows interest in usually turns out to be the villain, and is then never mentioned again, which makes the Hand Wave explanation of Sabrina leaving the team to get married rather inexplicable.
 * In one episode Kelly is shown to be in a loving relationship with an obviously nice, decent man, but she has to end it because she has to go and work undercover. He doesn't know what she does for a living so she ends it by hinting that she no longer cares for him. However, it's clear her heart is breaking as she says it.
 * The vast revolving cast of the main characters' love interests in Seinfeld. Often Lampshaded as examples of how dysfunctional the core cast are.
 * The only subversions would be Susan (for George) and Puddy (for Elaine). Then again,  and Puddy tells Elaine he will not wait for her in the finale. Even Jerry's fiance only lasts one episode (appearing briefly in a flashback sequence in the next one to explain that they mutually dumped each other).
 * Mariette in the fourth episode of Horatio Hornblower. Has a brief love affair with the hero, then gets shot just as she's escaping with him and is never mentioned again.
 * Although not nearly as prevalent as in Michael Landon's earlier series Bonanza, there were scattered episodes of Little House On the Prairie featuring tragic heroines coming into contact with a male teen-aged character.
 * The best example is Sylvia, Albert's girlfriend in the two-parter named for her that aired in early 1981. Sylvia lives in a horrifying, cold world -- she is teased mercilessly at school because of her early puberty, she is stalked by and impregnated by a rapist, her father calls her a whore, and Mrs. Olesen spreads malicious gossip suggesting that Albert had gotten her pregnant -- and Albert her only hope of happiness. Alas, even this is taken away from her when the rapist finds her hiding in a barn (Albert unknowningly reveals her whereabouts) and returns to rape her a second time; She tries to flee by running up a rickety ladder, but a rotted step breaks under Sylvia's weight and she falls to her death; however, death does not come about until after she is brought home, and she and Albert are allowed to share tender words.
 * The titular character from Merlin had Freya, a Mysterious Waif who is introduced and dies in the same episode - though she pops back occasionally as the Lady of the Lake.

Newspaper Comics

 * Parodied in a Dilbert strip where the title character comments it's strange he has a girlfriend, and that it reminds him of Star Trek episodes where Kirk falls in love and you know she'll end up dying horribly -- meanwhile, a flaming meteorite hits the ground just behind them and the girlfriend looks freaked out. Ironically, she goes on to dump him because he isn't as fun to be around anymore. Maybe she only loved him for the meteors?

Western Animation
"Sokka: My first girlfriend turned into the moon. : That's rough, buddy."
 * Sokka got one of these in Avatar: The Last Airbender with Yue. Although technically she Ascended To A Higher Plane Of Existence as the moon. She is, however, mentioned more than once and the memory of her "departure" does stay with Sokka.


 * Played with on Samurai Jack, where the temporary love (or respect) interest
 * The girls in Totally Spies rarely keep a love interest for more than one episode due to Status Quo Is God.