Bathtub Bonding

This is when two characters (most of the time Heterosexual Life Partners; rarely are they ever Platonic Life Partners, though this can be used if the Platonic Life Partners in question have enough unresolved sexual tension between them to make them popular targets for shipping and the writer wants to do a scene where said unresolved sexual tension comes to a head) take a bath together and usually converse. This causes them to really get to know each other better or become better friends. Usually either really significant moments of the plot are discussed or one character's past is revealed in a Bathtub Bonding scene. Relatively common in anime due to the Japanese concept of "skinship". At least two characters have to share a bathtub in order to qualify for this trope.

Anime and Manga

 * In episode 24 of Neon Genesis Evangelion,  gets into the bath with Shinji. What follows is the most important step in their relationship development.
 * In the 28th episode of Nana, Hachi jumps into Nana's bath, which at first becomes uncomfortable for Nana, but then not so much.
 * Kagome and Sango have done this in episode 29 of Inuyasha and in the second movie. Neither instance was actually in a bathtub, but rather in a hot spring.
 * It is done in Butt-Attack Punisher Girl Gautaman R but to an uncomfortable extent.
 * Rushuna and Mikan bathtub bond in the ninth episode of Grenadier.
 * Miina and Karen do this in pretty much every episode of Please Twins
 * Uruka and Saki bond in a bubble bath in episodes 5 and 6 of Steel Angel Kurumi 2.
 * There is a bathtub bonding scene with Sakura in Street Fighter Alpha: Generations.
 * Hime-chan and Pokota, her magical talking stuff toy, do this in the seventh episode when talking about how to deal with Himeko's current problem.
 * Nadia from Nadia: The Secret of Blue Water bathtub bonds with Electra in episode 20. She also bonds with Grandis in a bubble bath in episode 33.
 * In the eighth episode of The Familiar of Zero, it is done with Saito and Siesta, who are opposite genders. Surprisingly enough, the guy was the uncomfortable one.
 * More specifically, Saito just built a hot tub, and Siesta has a crush on him. He was planning on being there alone, and is punished by his master (and local Tsundere) Louise when he shows interest in other women. He has feelings for Siesta, but is in a Harem Series, so it's always awkward for him.
 * This happens a lot in Mahou Sensei Negima, although there usually aren't any romantic undertones due to the fact that Negi is ten, and Oblivious to Love. So far, he's gone through bath bonding with Asuna, Kaede, and Evangeline. Notably Eva, vamp that she is, wanted it to be sexual but failed miserably because, as stated above, Negi hasn't reached puberty yet. (Technically, neither has Eva.)
 * Magical Girl Lyrical Nanoha
 * Attempted by Fate in the first Sound Stage of Magical Girl Lyrical Nanoha A's, though Amy interrupted her before she could gather up her courage to ask Nanoha to go to the bath tub with her.
 * On the other hand, her adopted daughter Caro was a lot less nervous about this in the first Sound Stage of StrikerS. She just jumped right into Erio's side of the Hot Springs (kids under 11 are allowed to go anywhere they want) to do some serious bonding with him, much to Erio's horror and embarassment.
 * Fate also likes bathing with her children, and in one of the one-shots, gets quite disappointed when Vivio expresses a desire to take a bath by herself in order to appear grown-up.
 * Male example: A chapter of the Keroro Gunsou manga had Fuyuki and Keroro doing this. Then members of the supporting cast show up and try to join in... meanwhile, Natsumi is feeling left out but refuses to admit it.
 * Done in the third, seventh and eighth episode of Seikon no Qwaser.
 * The 10th episode of Omamori Himari does this.
 * In Hidamari Sketch, Miyako practically forces her way into Yuno's bath, on account of her having no running water in her own apartment (as she kept forgetting to pay the water bills. Poor, shy Yuno doesn't know what hits her. Still, it pays off, since both girls are the best of friends ever after.
 * Goku and Gohan do this while training in the Hyperbolic Time Chamber in Dragonball Z.
 * Lucy and Kana share a bath in Fairy Tail. Lampshaded when Kana asks if Lucy usually fits two to a bath, and Lucy counters by asking if Kana usually breaks into other people's houses. Characters breaking into Lucy's house is something of a running gag.
 * Hinako and Hiyoko from the Training with Hinako series share a bath and wash each other.
 * Akane and Mikoto in Kämpfer. Bonus points for Mikoto's blatantly sensual poses and Akane's shyness about looking at her.
 * In A Little Snow Fairy Sugar, Sugar and Saga often share a bath to discuss the day's events, with pint-sized Sugar sitting on Saga's knees to keep from drowning. Saga also uses the bath to bond with Kanon.
 * Nanako and Mariko share one of these scenes in Oniisama e....
 * In the first episode of Zetman, after taking the homeless ten-year-old Jin into her home, Akemi climbs into the bath with him to comfort him in his grief over the death of his adopted grandfather.
 * Happens often in Popotan, the most archetypical example being between Mai and Konami's daughter (also named Mai) in episode 9.
 * In the original Birdy the Mighty, one episode has Tsutomu's father head to the bath to join him in some "father-son naked bonding time", as he puts it. Tsutomu's sister naturally has a WTF reaction.

Comic Books

 * Used at least once in X-Force between Cable and Domino.
 * Sam and Max Freelance Police: Sam and Max apparently took baths together when they were kids, according to photos in their office.
 * Faith and Gigi, the slayer planning to kill Buffy, in Buffy the Vampire Slayer, season 8.

Fan Works

 * In Nanoha as Divergence, a Lyrical Nanoha fic, Vita and Yuuno did that while waiting for others to come, and Vita learned about the origin of his scars and it's seems that they start to trust each other after that (even having Not a Date five days later). Also mentioned with name in the omake section.
 * A throwaway gag in The Weekly Hyrule News is Link and Dark showering together; it's mentioned more in the Dead Fic sequel. Nothing significant happens except to highlight Dark's Keet-like personality, and that they're comfortable around each other.
 * This short Withnail and I fic. However, they don't really bond.

Films -- Live-Action
"Tom: I'm cold, can I get in? Dickie: ... No. Tom: (embarrassed) I didn't mean with you in it."
 * Done a couple times in the movie Heavenly Creatures.
 * Used in the movie Tart.
 * Done in the movie Ballet Shoes.
 * Andrew and Sam in Garden State, albeit without water in the tub.
 * In the film Shanghai Noon, Roy and Chon spend some time bonding in the bath. Technically most of this happens while they are in separate tubs, but the scene is shot to give the impression of shared space, and then they end up in the same tub until Roy's token woman comes to end the fun and reinforce the Not Gay.
 * Narrowly averted in The Talented Mr. Ripley when Tom Ripley and Dickie Greenleaf play chess together while Dickie is in the bath. Dickie expresses his dissatisfaction with being an only child, while Tom's lingering stares again alert the viewer to Tom's growing fascination with Dickie.


 * Harry and Lloyd did it in Dumb and Dumber, and it was a heart-shaped bathtub to boot!
 * Laure and her sister in Tomboy. Helped by the fact that she's 10 year old and her sister 6.
 * Probably the most famous animated sketch in German TV is Loriots "Two men in a bathtube". Even after more than 30 years.

Literature

 * In A Song of Ice and Fire, Jaime and Brienne share a bath during which he explains why he killed the mad king Aerys to her, his reason being something that he hasn't really told others before.
 * The plot of the Maisy picture book Maisy Takes a Bath, later adapted for the animated series, was that Maisy Mouse wanted to take a bath, but her friend Tallulah the chicken kept knocking on her door, wanting her to come out and play. At the end of the story, Tallulah hopped in the bath with Maisy and they had fun together.

Live-Action TV

 * Happens once or twice in Kyle XY between Kyle and other characters (usually Amanda or Jessie). Notably there isn't ever water in the tub. He sleeps in it.
 * Several episodes of Xena: Warrior Princess have Xena and Gabrielle sharing a bath. Slash fans rejoiced.
 * An episode of Hercules: The Legendary Journeys had Autolycus and Salmoneus sharing a bath. Slash fans did not rejoice.
 * Clips from Season 4 of Top Chef Reunions showed Richard Blais and Dale Talde in the bathtub together.
 * Wataru from Kamen Rider Kiva has taken at least one bath with almost every single character of importance in the series. His Dad Otoya did the same thing 22 years earlier.
 * Monica and Chandler in Friends.
 * Saturday Night Live - recurring character Simon (Mike Myers) was a small English child who hosted his show in the bathtub - one installment had him sharing the tub with an American kid (Danny De Vito).

Video Games

 * Sam and Max Freelance Police: Sam and Max apparently took baths together when they were kids, according to photos in their office.
 * In Kanon, Yuuichi can try to get in the bath with Makoto. Twice.
 * In the anime, suggesting this is Yuuichi's immediate recovery upon accidentally walking in on Makoto naked. She doesn't take it well.

Western Animation

 * The Simpsons: The season six episode "Grampa vs. Sexual Inadequacy" has Homer and Marge trying to pump some new blood into their tired love life by having a candlelit bath for two. This doesn't work as the tub is too small, Homer is too fat, and it ends with the two of them stuck in the tub in complete darkness, yelling for the kids to help them out.
 * Family Guy
 * Similarly, on the movie "Stewie Griffin: The Untold Story", Peter and Lois get in the tub together. Peter has to move his big, fat stomach out of the way so that she can get into the tub. He holds his stomach out of the way until she's comfortable, and then he lets go of his stomach and it smacks Lois in the face and her head rebounds off the faucet. The kids interrupt the bath with their inane arguing, so Peter and Lois decide to teach the kids how to date so they can get some alone time. The scene ends with Lois trying to lean in to kiss Peter, only to slip out of the tub, and Peter to notice that she's bleeding from a possible head injury.
 * Subverted with Stewie and Meg. Stewie farts in the tub. They laugh. Meg farts in the tub. They laugh. Meg accidentally queefs. Stewie screams and hightails it out of the tub.
 * American Dad had a particularly Squicky one on the episode, "Oedipal Panties". After Roger tells Francine that there are no signs of disturbing togetherness between Stan and his mother, Francine asks Roger to go in the bathroom and get her some aspirin, which Roger accepts since he's going through a "white month" (read: he's exercising and cleansing his body of all the drugs, alcohol, and junk food he regularly consumes) and needs an excuse to work his leg muscles. When Roger opens the door, he sees Stan and his mother in the bath, with Stan singing a variant of "What Do You Do With a Drunken Sailor?" and washing his mom. A commercial break later, Roger can be seen traumatized and holding a cup of (what can only assumed to be) booze.
 * The animated sketch Die Herren im Bad (The Gentlemen in the Bath) by the German humorist Loriot shows two gentlemen in the bathtub of a hotel room. Their conversation, while relatively well-mannered, is more bickering rather than bonding, though.