What Measure Is a Humanoid?

This is where there's something romantic going on between a human and something that, for whatever reason, looks equally human but is actually nonhuman (not Petting Zoo People, just a nonhuman that spends most of the time looking human). The romance element can be anything from subtext to full blown relationships, and for some reason are never treated as if there's any reason why they should be squicky at all. In fact, in some cases, they actually come across as sweet and touching, and the dominant thought on the readers mind is usually "awww," which probably wouldn't be the case if the nonhuman in question wasn't usually human-shaped.

See also some cases of Interspecies Romance, Robosexual.

Anime and Manga

 * Pet Shop of Horrors did this a few times, usually more towards the subtext end of the scale.
 * This was more or less the entire premise of Guru Guru Pon Chan.
 * Ranma ½, with the Musk Dynasty, who turned animals into women using the Springs in order to have children with them.
 * Angel Tales (Tenshi no Shippo).
 * Pretty Cure 5.
 * Pretty much all the relationships between owners and their persocoms in Chobits.
 * Tsukihime: because "a cat is fine, too".
 * In Man's Best Friend, a Yaoi manga by Kazusa Takashima, a dog falls in love with his teenage-boy owner and gains the ability to transform into a hunky man.
 * Chibi-Usa and Pegasus/Helios from Sailor Moon.
 * Also, Luna and Kakeru from same.
 * There are the homunculi from Fullmetal Alchemist.
 * Inuyasha, being a half youkai, had a human mother and a youkai father.
 * Although not canonically a relationship, the Sesshoumaru and Rin shippers that read into subtexts fit this trope. Despite that Rin is only the Morality Pet in the series. Also note that during his introduction (that took three episodes), Sesshoumaru transformed into a giant dog that Inuyasha said was his true form. Also, with Myouga pointing out that their father used illusions or spells to appear human...yeah it's really a support of Giant Dog on Little Human Chew Toy if you discount the human transformation.
 * Since familiars in Magical Girl Lyrical Nanoha were originally animals such as cats or wolves, pretty much any case where a familiar exhibits feelings for a human and vice versa falls under this, such as the Les Yay between Arf and Fate, or Lotte Lieze showing much affection towards Chrono.
 * The anime Soul Eater features weapons such as scythes, swords and guns that have humanoid forms. And can go so far as to be able to reproduce with humans. Maka, one of the main characters, is a progeny of a human/weapon relationship. Does not apply at all for the weapons. They are all humans, they are just humans who have special powers. Although this may somewhat apply with the witches, they may be immortal therefore not human, and it does apply with Blair the cat.
 * Also applies to the shinigami, who are not human, but in Kid's case just look as though they are (not so much for Shinigami, but if Mosquito is to be believed he either can do or has done in the past).
 * In The Twelve Kingdoms (both anime and novel) there's a fair bit of subtext between Rakushun and Youko...and Rakushun is basically a giant, vaguely humanoid rat (he's pretty much just a rodent of unusually large size that can stand on his hind legs) who can turn into a human at will, though he prefers his rat form. There's also a not-so-implied unrequited love between the former Queen of Kei and Keiki, the shape-shifting Unicorn...and then there are in turn shippers who swear by a Keikix Youko coupling. (Personally, this troper has never seen the chemistry, but there have certainly been less likely couplings.)
 * A filler episode of The Slayers has a man fall in love with a fish person. They want to find a potion that will 'allow them to live together', thinking this means that it will turn the fish-woman into a human woman. While this is true, it also turns the man into a fish-man. They are perfectly happy with this.
 * Happens many times in Dragon Half. Vina's mother (a slime) fell in love with the king (since his dumpy head sort of looked like a slime) and used a potion to turn human... except their daughter was born as a slime too, and then has to use magic to (temporarily) maintain a human form. Rouche the knight meanwhile fell in love with the dragon he was sent to slay, Mana, and eloped with her. (Humorously, although she can turn almost-human, he appears to have fallen for her in her dragon form...) Mink wants to become human too, even though she's almost completely human except her wings, tail and horns (and super-strength), but this is mainly because her love interest is an overzealous dragon slayer.
 * The robots in Eve no Jikan suffer from this.
 * Spice and Wolf has this in spades.

Comic Books

 * I think that in one story, Krypto The Superdog turned into a human and formed a relationship with a woman.
 * Don't remember that, but there definitely was such a plot involving his colleague Comet the Super-Horse. (If I have this right, it turns out that Comet was really a centaur who'd been cursed so that at any one time he had to be all horse or all man. I don't know if that helps, really.)
 * As I recall Comet was a lesbian cursed to be a male horse for the rest of her life.
 * I don't know about the lesbian part, but Comet did had a relationship. With Supergirl. Yeah.
 * Lesbian Comet is the Post-Crisis version, who was a lesbian comedienne who'd combined with a male superhero with horse-DNA to form an Earth Angel in the same way as Supergirl combined with Linda Danvers. (S)he could alternate between the two forms. Supergirl was attracted to Comet, but somewhat taken aback by Andi.
 * Alan Moore once wrote a story about Swamp Thing's girlfriend noting that Lois and Superman have essentially the same relationship as they do.
 * After she got arrested for "Crimes against nature", leading to Swamp Thing using his plant powers to turn Gotham City into a jungle, Batman pointed this out to the mayor, who panicked and dropped the charges.
 * Beast's girlfriend left him when he went from blue-hairy-ape-man-thing to blue-hairy-cat-man-thing, because even with all the fantastic racism that was the point that people started comparing their relationship to bestiality.
 * Later, poor Beast gets feelings for a cat-girl, who actually turned out to be more cat then girl. Seems mutancy is not just restricted to homo sapiens.
 * XXXenophile goes out of its way to transform one housecat into a human before getting him involved with a human woman. This may have been more about scale than anything else, given that the same woman gets involved with a shapechanging Fairie Queen that goes much, much further from the typical form factor trying to Squick her out.
 * This is also the comic which features a human having sex with a centaur several times before the centaur had sex (offscreen) with a horse—the 'curse' of being part horse transferred with sex, so the horse wound up with six legs afterwards.
 * Tank Girl gives us the relationship between the heroine and her mutant kangaroo boyfriend Booga. He behaves pretty much like any human, and the issue of their Interspecies Romance is rarely discussed.

Literature
""You see, a yennork would go off and be a human or be a wolf but they'd still be carrying the werewolf...blood, an then they'd marry and have children...or pups...and, well, that's where the fairy-tale monsters come from. People with a bit of wolf and wolves with that extra capacity for violence that is so very human." She sighed, and glanced momentarily at Gavin."
 * Jim Butcher's Fool Moon, in covering the range of Our Werewolves Are Different, includes wolfweres (wolves that can take human form rather than the other way around).
 * Poledra in the Belgariad. She's a wolf, who takes the form of a human because she loves Belgarath, a human who can take the form of a wolf. And, no, we don't get any explanation for why she is the only wolf known able to do this and live for thousands of years. Her expressions on the subject, irritating as they are ("what is time to a wolf?" Screw you), seem to imply they all could.
 * Another likely explanation is that wolves, like humans, have the potential to become sorcerers, who get functional immortality and Voluntary Shapeshifting as inherent abilities. Poledra is either the only wolf to really get the hang of her powers, or the only one to actually take an interest in human affairs.
 * There's another example from the Trickster duology written by Tamora Pierce - Nawat is a crow who becomes human after falling in love with the protagonist. At first he continues to act somewhat like a crow, but she doesn't start to return his affections until some time later, once he's started to act more human.
 * Terry Pratchett, of course, plays with this in Discworld.
 * Ludmilla Cake and Lupin in Reaper Man. She's a human who turns into a Wolf Woman at full moon. He's a wolf who turns humanoid at full moon. They apparently have a relationship for one week a month, and the rest of the time Lupin is kind of Ludmilla's mother's pet dog. Which is a lot squickier written like that than it was in the book...
 * Another werewolf, Sergeant Angua, has a romantic relationship with Carrot, a human who thinks he's a dwarf. The books mention that relationships between humans and werewolves are usually extremely difficult, but they manage to make it work.
 * Inverted The Fifth Elephant, where a wolf called Gavin (well, he once ate someone named Gavin) is said to have had a very Carrot-like relationship with Angua. The Squick mitigation comes less from him being a smart wolf, and more Angua not being human all of the time she's with him.
 * That, and the fact that it's implied that Gavin is the descendant of a yennork—a werewolf who isn't able to morph.


 * Nanny Ogg's pet cat Greebo, in Witches Abroad, picked up a new skill: he can turn into his human male equivalent, and invokes All Girls Want Bad Boys. He retained the skill, and uses it again in Maskerade.
 * Any one person that's in love with a werewolf in the Twilight universe. Sure, they originally were human so it may be a subversion in that regards, but they're still large wolf like things that don't really look like wolves in the movies.

Live-Action TV

 * Numerous relationships between humans and aliens on Star Trek. Captain Kirk was famous for fucking aliens " going coming where no man has gone before".
 * And copied on Affectionate Parody Galaxy Quest with "Jane Doe", who is actually a tentacle monster.
 * Both subverted and played straight in Farscape. John's dad tells Aeryn outright that he isn't bothered by her relationship with John since he doesn't think of her as an alien. However, in the TV program they intercept from Earth later, there is quite a lot of debate over whether or not Aeryn is pregnant with John's child and how Squicky it would be if she was.
 * In Buffy the Vampire Slayer we have Buffy who has relationships with vampires. And it's an ongoing joke with Xander that demons are attracted to him.

Oral Tradition, Folklore, Myths and Legends

 * Fox maidens, usually malicious (Everythings Foxier With Foxes) are common in Chinese, Japanese, and Korean mythology. Several examples are found in Strange Stories from a Chinese Studio (''Liao Zhai Zhi Yi") by Pu Songling.
 * Rabbit maidens, such as the one in the Cantonese opera Tryst with a White Rabbit, are usually benign.
 * Also celebrated is The Legend of the White Snake: a snake spirit falls in love with the student Xu-Xian. A Knight Templar type monk called Fa-Hai intervenes, not because she is evil, but simply because she is non-human. Fa-Hai's meddling did more harm than good.
 * In South America there is the legend of the Encantados, pink river dolphins that change into men so they can seduce and/or abduct human women. Unexplained pregnancies? Hey, blame the dolphins. Who else could be responsible?
 * Older Than Feudalism: Zeus in the Greek Myths, often changed into animals and seduced women. These relationships often produced children who were harassed or even killed by his wife, Hera. Helen of Troy—the most beautiful woman in the world—is likely half-swan, since that was the form Zeus took when he raped her mother. Some versions of her birth involve her hatching from an egg.
 * Selkies? Swan-maidens?

Video Games

 * Human girls sometimes show interest in any incarnations of Ryu, the protagonist of the Breath of Fire series. The only thing is that his real form is a dragon.
 * The same goes for Fou-Lu, the main antagonist of Breath of Fire 4, where there is a side story that shows a human girl falling in love with him. He's also a dragon.
 * Ryu in Breath of Fire 2 is the son of a dragon and a human man.
 * in Kanon is actually a fox.
 * Similarly, in Clannad, the lover of  who turned out to be . Both are played with as much Tear Jerker potential as possible.
 * A robot falls in love with the protagonist of Da Capo in one of the extra two routes. Apparently this sort of thing is intended to happen as she apparently has a hymen to break and gets pleasure from sex. But um until that point in the story...
 * Sora of Ever 17 falls in love with Takeshi. While he doesn't really reciprocate, he does find her very beautiful and the characters in story go awww... as well.

Web Comics

 * In Hanna Is Not a Boy's Name, Veser is the Half-Human Hybrid of a human and a selkie (see above). Going by the legend, though, she's not really a willing participant. Veser's Parental Substitute was also in love with her. It's a pretty dysfunctional family.
 * One subplot in The Order of the Stick explores the nature of goblins relative to other races, and goes into detail in strip 1232, "Equity Options".

Western Animation

 * The Last Unicorn is fully sentient in her original form, so it may not fully count. But in a poignant scene there's still a slight moment of Squick/hilarity when Lir, who's in love with her as a human finds out who she really is and says "Unicorn, mermaid, sorceress, no name you could give her would surprise or frighten me. I love whom I love." Schmendrick says "Well, that's a very nice sentiment, but when I turn her back into her proper shape..." and Lir just repeats stonily: "I LOVE WHOM I LOVE."
 * Inverted in Beauty and The Beast, although that one still gets lots of d'awwww....
 * Adventure Time. The fact that Finn is the ONLY seeming human in the world at the moment, coupled with that he's lusted after by a whole harem of weird princesses. Most notable relationships he's been associated with is him and Bubblegum (candy person) and Marceline (vampire/demon/human), though.