How does a TV show demonstrate that Bob and Alice are a couple? How to do it quickly and without making a big deal about it? Simple, Alice wears Bob's jacket. If Bob's some kind of athlete, expect it to be his letterman jacket.
This is Truth in Television, and not limited to jackets. A little research indicates that the reason girls do this is fourfold. First, they're big and comfy. Second, it marks both of them as taken. Third, it's like a day-long hug. Finally, it smells like him.
This can be more than just an "I like this and I like you" gesture. It can be a symbol of commitment. Sometimes it's a class ring, or a necklace, or a favorite hat. The point is that one partner is wearing something that until then was always seen on the other, so that the world knows they're a couple.
It need not only be women wearing something of their men's collection. A man is less likely to wear his girlfriend's clothing, but a token is often passed in that direction, as in Chivalric Romance when a man receives The Lady's Favour, usually in the form of a scarf or other small piece.
The Japanese term is kare-shatsu.
See also to You Must Be Cold, which can be a one-time romantic gesture and serve as part of a Ship Tease. Her Boyfriend's Jacket is a long-term appropriation of clothing to demonstrate a relationship. Also related to Sexy Shirt Switch, where she wears other articles of clothing after sex. Both are signs of intimacy. Sexy Shirt Switch is sexual intimacy, Her Boyfriends Jacket is emotional intimacy.
- There's a style of clothing in fashion known as "boyfriend clothing". It's clothing that was designed for men and redesigned for women. It looks like typical men's fashion, but with a looser fit more comfortable for women. From the other wiki, "The origin of boyfriend fashion is literally borrowing and wearing a boyfriend's clothes—his distressed jeans, his band tees, his dress shirts, his blazers, his cardigan. The trend expanded in 2009 when actress Katie Holmes was spotted in public wearing Tom Cruise's slouchy jeans after a Broadway rehearsal; other celebrities such as Reese Witherspoon, Rachel Bilson, Sarah Jessica Parker, and others began to follow the trend. From there, many brands such as Gap, Forever 21 and H&M began to create boyfriend fashion products or men's-inspired fashion."
- The 1980s "I was just thinking of you" Arrow shirt commercial combined this trope with Sex Sells by showing a young wife first sniffing then wearing one of her husband's Arrow shirts while he's away on a business trip.
- A recent Bank advert in England has a man needing to use the Bank's new withdraw-via-a-code-we-send-you-if-you-lose-your-card system because he accidentally left his wallet in his jacket... and his jacket on Jackie.
- In the final act of AKIRA, Kei is wearing Kaneda's red biker jacket.
- In Last Exile, after Claus and Tatiana crash land in the desert, he offers her some spare coveralls as a change of clothes. When they get back to the Silvana, Claus' old friend Lavie sees Tatiana wearing his clothes and she begins to fear this is happening.
- Yu-Gi-Oh!: During the Virtual World arc, Yugi lends Tea his jacket.
- Irresponsible Captain Tylor. Empress Azalyn wears Tylor's UPSF coat with smiley face button while he's her captive and 'pet', in a sign that she's fallen for him.
- While they aren't actually dating, the artist for the manga version of Durarara!! certainly likes to draw Namie Yagiri wearing her employer Izaya Orihara's jacket.
- In the X-Wing Series, the first indication of a relationship starting between Corran and Mirax is her walking into the fighter bay wearing his flight jacket. She even pulls it closer around her when she notices one of the female pilots glaring at her. Said female pilot happened to be also interested in Corran.
- A variation in Death Vigil: Issue 8 confirms that Sam and Bernie are in love after a Big Damn Kiss, and a reveal it's not their first. Immediately after Bernie goes out to confront the Thorn and buy time for the rest of the Vigil to put their plan to defeat it into motion, and alters her robes to display Sam's skull and crossbones logo while the Scythe takes on the appearance of his veilrippers.
- Why And Were, a Discworld fanfic, has a scene where Assassin Johanna dons Wizard Ponder Stibbons' wizarding robes. Partly because they're warm, comfortable, and smell slightly of Ponder (a big plus in the early stages of a relationship), but mainly because she'd otherwise have had to answer the door naked.
- The magnificently funny Ranma ½ fanfic Crossed Wires spoofs this trope when Ranma in girl mode has to borrow Ryouga's clothes, including his distinctive shirt, and everyone immediately assumes this trope is now in play. Hilarity Ensues.
- Many Kim Possible fanfics depict Kim using one of Ron's red hockey jerseys as sleepwear.
- Two variations are used in the Facing the Future Series. The first was when Sam used one of Danny's jumpsuits in her transformation into Sam Tasma. While she mostly did it because Danny was the same size as her, she did get a thrill out of wearing Danny's clothes at the same time. The second was when Sam dressed like Danny for Halloween mostly to creep Tucker and Valerie out by making out with Danny while looking like him.
- A rather infamous Hetalia doujinshii has Hungary completely naked in its cover, save for Prussia's blue and red military jacket.
- The ending of The Legend of Korra sparked plenty of fanart and fiction involving Korra wearing Asami's jacket. See for yourself.
- In the Batman Beyond episode Dead Man's Hand, which introduces The Royal Flush Gang, Terry meets Melanie Walker and, at one point, gives her his jacket. In the fanfiction Reunited, which is set several years later and depicts the reunion and rekindling of the romance between the two, she still has the jacket, and is in fact wearing it when she first appears in the second chapter.
- In Chapter 36 of Ghosts of the Past, at one point Harry notices that his friend (and Most-Definitely-Not-A-Girlfriend) Carol is wearing what appear to be his boxers.
- A curious variant exists in the Twice Upon An Age series of Dragon Age: Inquisition fanfics. When Bethany Hawke joins the Inquisition late in the first story, it's observed that she wears a heavy-looking ring on a chain around her neck, but no details are given. A side story reveals that this is actually the signet ring of House Tethras, sent to her by Varric for "safekeeping." Eventually other characters figure out what the ring really is, but nobody seems to be quite sure what her wearing it means - including both herself and the person who gave it to her.
- Shelly in Sin City wears Dwight's shirt when Jackie Boy arrives at her apartment. He is not amused.
- In Jarhead, the girlfriend of one of the marines keeps sending him sexy photos of her wearing his uniform jackets (and nothing else). One of the other marines eventually asks if she has any clothing of her own.
- Cyberthriller The Net has Angela Bennett wrap herself with Jack Devlin's sport coat while aboard his boat. When she finds a gun with a silencer in one pocket, she begins to suspect that Jack intends to murder her.
- Cherry in Planet Terror wears El Ray's leather jacket, much to his chagrin, since she left him and he was searching for it for months.
- Parodied in Scary Movie. While Ray and Brenda are chilling out she's wearing his football shirt, which turns him on. He asks her to wear more of his football clothing, including his pads and helmet to Brenda's increasing confusion. Though he does accidentally call her "Brendan" at one point.
- Over the course of The Force Awakens, both Finn and Rey end up wearing Poe's leather jacket. The fans have noticed.
Poe: Keep it. It suits you.
- In The Dark Side of Nowhere, there's a gender reversal of this. Girls wearing their boyfriend's letter jacket to signify that they are together is a custom in their high-school, but when protagonist Jason gets together with his athletic tomboy love interest, he wears her letter jacket.
- In his book Couplehood, Paul Reiser complains about this practice (Link!)...
"And of course, later, it's freezing, and she's huddled in my jacket, and I, who knew to bring a jacket, am wearing no jacket. And the kicker is: It's not like my jacket looks so good on her anyway. It certainly looks worse than whatever jacket of her own she would have put on."
- A major Ship Tease moment in A Song of Ice and Fire is when a distraught Sandor Clegane tears off his Kingsguard cloak and abandons it in Sansa Stark's room. She picks up the cloak and wraps herself in it (this has added Rule of Symbolism, as in a Westerosi wedding the husband wraps his wife in his cloak) and later hides the cloak in a chest.
She could not say why she kept it.
- Played for Laughs in War Junkie by Jon Steele. Steele is dating his producer, and at one point lists all the clothes she's nicked off him. "Do you know how much this relationship has cost me in clothes alone?"
- At one point in The King of Attolia Eugenides is told there is an urgent matter he needs to address and he half-halfheartedly notes he's wearing the queen's floral embroidered nightshirt in an attempt to delay it.
Irene: Your attendants. I have spoken to them. You will speak to them as well.
Eugenides: Ah. They have seen me in my nightshirt. Not in your nightshirt, though.
- Doctor Who:
- In "The Chase", it's revealed Ian likes to wear his Implied Love Interest Barbara's cardigan at times.
- In a platonic example, the Fourth Doctor's companions liked to wear parts of his outfit when they could. In "Terror of the Zygons", Sarah wears his hat and Harry his scarf; in "The Invisible Enemy", Leela wears his hat; and Romana II would often 'borrow' his scarf or wear a copy of his outfit, sometimes in pink.
- Amy Pond, disconsolate after the death of the Doctor in "The Wedding of River Song", is shown consoling herself by drinking wine on her patio, wearing the Letterman's jacket Rory was sporting in "Let's Kill Hitler".
- Buffy the Vampire Slayer:
- Angel gives Buffy his leather jacket in the fourth episode, "Teacher's Pet". She wears it for the rest of the first season, albeit with the sleeves rolled up. They're not a couple yet, but when, at the end of the episode, he says that "it looks better on [her]", she knows she's fallen for him.
- Tara wears Willow's sweater in the fourth-season episode "New Moon Rising", which precipitates the episode's trouble.
- In "Tabula Rasa" Xander lends Willow his jacket because it's cold, leading to comical misunderstandings when they have their memories wiped and assume this trope is in play.
- Discussed and subverted in the second season. Finn and Rachel think that Sam is dating Kurt after they see him wearing Kurt's jacket, specifically citing the common practice among girls of wearing their boyfriend's jackets. It turns out that Sam's dad lost his job, resulting in the Evans family becoming so poor that they're staying in a hotel room. The jacket in question was part of a handout package consisting of Kurt's old clothes given specifically with the intent of helping out Sam's family.
- In the fourth season, a Betty and Veronica Love Triangle is established between Marley, Kitty, and Jake when Marley spends a few days wearing Jake's coat (from a You Must Be Cold moment) and Kitty demands it as this trope when she and Jake start dating (though he doesn't like labels).
- An episode of My Family involves Janey being given her boyfriend's jacket and taking a liking to it so much she tries to avoid giving it back even after dumping him. Eventually he tricks her into giving it back, though she manages to coax it out of him by dating him again.
- This becomes a plot device in an episode of Leave It to Beaver, in which Mary-Ellen Rogers wants to impress her friends and charms Wally into letting her wear his Letterman sweater.
- In the episode "The Little Kicks" of Seinfeld, Anna returns to work at the J. Peterman Catalog at one point, wearing George's Yankees jacket, after Elaine warned her to stay away from him on the grounds that he's "a bad seed".
- On General Hospital, varsity athlete Jason gives Karen his letter jacket as a means of making their relationship official. . . and she returns it when she breaks up with him.
- On One Life to Live, Jason loans Marty his leather jacket. When his girlfriend Dorian sees Marty wearing the jacket, she flies into a jealous rage. This is not helped by Marty's taunting her (she's not interested in Jason, but she dislikes Dorian and thinks she's bad for him).
- Jessica Jones: Jessica's trademark leather jacket is revealed in season 2 to be one she acquired on the night that she first hooked up with Stirling.
- A near universal trope in the early-1960s fad for teen death songs was the presence of a lover's class ring.
- "Leader of the Pack" by the Shangri-Las starts with the narrator's classmates asking her if she's "really going out with him," only for her to reveal that she had been with him until he had died in a horrific motorcycle accident.
- In Mark Dinning's "Teen Angel", the girl dies by going back across an active railroad crossing to grab the class ring she'd dropped, and the narration goes "they say they found my high school ring clutched in your fingers, tight".
- A contemporary parody of the genre by skiffle group The Mark III, "Valerie", makes a point of establishing the girl has the boy's class ring to indicate what kind of song it's going to be, so the listener isn't surprised when she dies by slipping in the bathtub.
- Pretty much the only times the class ring isn't mentioned is if it's a genre piece, like one of the many Western-themed teen death songs.
- In "It's My Party (And I'll Cry If I Want To)," the narrator is devastated when her boyfriend Johnny shows up at her birthday party with their classmate Judy. "Oh, what a birthday surprise/Judy's wearing his ring!"
- Blue Mary in Fatal Fury. The boyfriend in question is deceased, though how was not elaborated on.
- Final Fantasy:
- During the course of Transistor you gain subtle hints about the main character Red's relationship with the voice in the Transistor (and former owner of the body that you find impaled by the Transistor at the very start of the game). She wears his jacket.
- Monster Prom: If the player makes a successful run in which Amira ends up with Scott, the Polaroid at the end of the credits will be one of them stargazing together, while she wears his jacket.
- In Antonio Vasquez's route of Havenfall Is For Lovers, Antonio puts his leather jacket on the heroine to protect her during a fire. She proceeds to wear the jacket on and off for the rest of the route, at one point waking up to find she's wrapped herself up in it in Antonio's absence, as an indication of the growing intimacy between them.
- Gunnerkrigg Court: In Chapter 14, Kat can be seen wearing the T-shirt of her brief love interest, Alistair, who left her his personal belongings after he had to turn into a bird and leave.
- In Questionable Content, Hannelore and Sven go on a fake date (because she never has), at the end of which she looks absolutely adorable wearing his hoodie against the cold.
- In Girl Genius, Zeetha wears Higgs' striped shirt when we see them after they hooked up - since there was a two and a half year timeskip between the hook-up and the audience seeing them, it's reasonable to assume they've graduated to a full relationship. When they're next on the same page as each other, we can see that they're wearing matching shirts.
Agatha: [heart-shaped speech bubble] ...Gil! Oh. It's his coat.
- After Agatha gets knocked out by a sleeping drug, as do several other characters, she falls on top of Gil - and when she wakes up several hours later she's still clutching his coat, even after he's been removed from it.
Violetta: Yeah - you wouldn't let go, so we just stole it off him!
- An episode of Pepper Ann had the title character start wearing Milo's ever-present hat so it would look like they were dating. To cope, Milo started wearing increasingly-ridiculous hats as the episode progressed.
- During the brief time they were dating in As Told by Ginger, Ginger wore Darrin's jacket.
- While two instances where Sam dressed up like Danny in Danny Phantom couldn't be considered this, the time they both had a shared dream where they were dating with Sam wearing Danny's football jacket (him being on the football team in the dream) could count as this. There's also the instance in the Grand Finale where Danny gives Sam the class ring he got from Jack, making them officially boyfriend and girlfriend.
- From Major Lazer, Ryland gives Penny his jacket at the end of "Vampire Weekend" as he lays dying.
- Batman Beyond Although the relationship doesn't last, Melanie wearing Terry's iconic jacket is a visual cue of how serious their whirlwind romance is. Terry's longtime girlfriend Dana is also spotted wearing the jacket on occasion in several different episodes.
- Futurama: In "The Sting", Leela, who has been having guilt-fueled dreams about Fry following his death, wakes up from a dream and finds she's wearing Fry's red jacket, convincing her that Fry might be alive somewhere. But when she shows it to her friends the next day, it's suddenly her own green jacket.