Either way, if the object of desire is particularly pleased, affectionate, or otherwise inclined, sometimes they'll give their admirer a kiss — or simply touch them. And the admirer will so treasure the moment and the memory that they want to keep the spot of the contact as it was at the moment forever — and that includes never washing it so as to avoid washing away the kiss (lipstick, etc). The Stock Phrase appears frequently enough to actually be its own trope. And when the "never washing it" declaration is taken to extremes, it almost always results in a Gross-Up Close-Up.
Sometimes the person is just saying it in dreamy-eyed appreciation. In other cases, they mean it literally, and will be seen days later, squeaky clean except for the kissed spot. Sometimes some wiseass will remind them that they seldom wash that part of their body anyhow, so it won't make much difference.
Of course this trope is not strictly limited to a spot where someone has been kissed. It can be a touch, or a handshake, or just a spot where the person stood. The kiss is just the most well known iteration.
It's also important to note that the recipient of the kiss usually thinks of the one kissing them as being a little out of their league, or else they hold them in such high esteem that a kiss is more like a divine bestowal than an actual kiss between people on the same romantic level.
- Oddly invoked in One Piece. Devil Fruit abilities are negated by water. Captain Van Der Dekken, owner of the Mark-Mark Fruit can target any two objects, one per hand, from anywhere. These targets are stored in his ability's memory until the hand is washed. As part of his master plan, he touched the target of his affection around 10 years ago, and hasn't washed his hand since. No mean feat, considering he is the first Fishman to have a Devil Fruit, and lives underwater.
- Tonari no Kashiwagi-san: After letting his crush Kotone wear the blazer for his winter uniform, Yuuta tries to keep his mom from washing it (she does so anyways).
- Sailor Moon has a simultaneous shot of Usagi kissing the pocket watch and Mamoru kissing the handkerchief.
- Doraemon: In "The Connection Cap", Noby uses the Connection Cap to meet the celebrity actress Serra Ivy. She holds Noby's hands, and he is very flattered and exclaims that he'll never wash his hands again. Serra comments that doing that would be very unsanitary.
- In Mafalda, one strip starts with Mafalda giving her father Ángel a kiss on the cheek right before he shaves. The next panel has Ángel smiling happily - with one un-shaved spot on his face.
- An episode of Full House involves Steph having this reaction to a kiss from her Celeb Crush.
- Alice (the '70s work com): Mel Sharples reacts this way when a famous person he admires visits his humble greasy spoon. He vows he will never wash the diner floor where his foot trod again. Waitress Vera quips, "You never wash it now."
- On The Brady Bunch, Marcia has this reaction after getting a kiss from Desi Arnaz, Jr.
- One episode of Family Ties sees Alex's nerdy best friend Skippy getting a kiss on the cheek from Mallory, on whom he's always had a crush. He says he'll never wash that cheek again, to which she replies, "Then you'll never get kissed again."
- The early sixties song "Ain't Gonna Wash for a Week", recorded most notably by Eddie Hodges and by the Brook Brothers.
- Doug: Doug, after Patty Mayonnaise has held his arm.
- Turned Up to Eleven in Family Guy. After a marriage counselor suggests that Peter and Lois start seeing other people, Peter looks up his old girlfriends, but all of them prove disastrous dates; one of them shows Peter her now rather grotesque hand that she hadn't washed in years after being kissed there, and the Stalker Shrine she built to the same object of obsession (Peter).
- Parodied, as always, by Futurama: After Leela kisses Fry's cheek, he declares, "I'm gonna continue never washing this cheek again."
- Hey Arnold!: Helga, after Arnold hugs her.
- "'It Girl'": Eugene, after Helga (currently famous as a supermodel) shoves him.
- My Little Pony: Friendship Is Magic, "The Secret of My Excess": Spike reacts this way to Rarity kissing him on the cheek... though he has said, "Eh, what does she know?" in response to Twilight warning him that he doesn't have a shot.
- The Simpsons: Bart makes this declaration after Laura (the next-door neighbor girl whom he has a crush on) spat in his hand as part of a prank. He sticks with it until it's practically black and covered with band-aids and old gum, but decides to clean it after an attempt touch Lisa causes his hand to get stuck on the dog's fur.
- SpongeBob SquarePants: Pearl shakes hands with her celebrity crush and swears to never wash the hand. Then Bubble Buddy comes along, shakes it, and the soap on him causes it to be sparkly clean, and Pearl bursts out sobbing.
- Muppet Babies: Gonzo finally gets a kiss on the nose from a grateful Piggy and says he'll never wash it again. Mercifully, the show ends right there.
- Lydia, disguised as a Femme Fatale (or perhaps a Femme Fatalized, considering), seductively pinches the ear of Beetlejuice. He privately declares, "I'll never wash this ear again — not that I ever did."
- The Grim Adventures of Billy & Mandy: After Eris is tricked into kissing Grim, he says he never washed his face before and won't start doing it now.
- Miraculous Ladybug: In "The Evillustrator", Adrien touches Marinette's shoulder, prompting her to say she'll never wash her coat again.
- Teen Titans Go!: When Starfire kisses Robin's hand, he vows to never wash it again - this after he scolded the other Titans for their poor hygiene. After months of being unwashed, the hand falls off and comes to life, which Robin thinks is due to the power of Starfire's kiss. In reality, the hand went unwashed for so long it had become zombified, and was now after the Titans' brains.
- My Life as a Teenage Robot: After meeting the Silver Shell and getting her metal body scorched by the blast of his jet boots, a love struck Jenny says she will never polish again.
- Vampirina: In "The Ghoul Guides Save the Day", Bob the Bigfoot autographs Edgar's shirt and Edgar says he'll never take it off again. His sister Poppy calls it "gross".