Even the Wombats Want Him

"Wild Empathy Check! WILD EMPATHY CHECK!"

—Belkar, fending off a charmed muskrat.

Animals falling in love with humans.

Examples of Even the Wombats Want Him include:

Anime and Manga

In Pokémon, Ash has had Chikorita(later Bayleef), Aipom and now Oshawott
- In Pokémon Heroes, Latias shows a good deal of affection toward Ash, to the point of (most likely) assuming the form of Bianca to give him a kiss on the cheek.
Kekkaishi: Madarao the dog-spirit used to be straight. Yet he fell in love in first sight with Hazama Tokimori, a male human, because Hazama was just that sexy.
The eponymous character of Hayate the Combat Butler, when dressed as a Catgirl, manages to earn the affection of Nagi's pet tiger Tama.
Ranma ½: Everybody wants Ranma Saotome. Everybody. Not even panda doodles are an exception!
In Ask Dr. Rin, Cynthia, a panda toy, falls in love with Asuka. No, it's never taken seriously, or else Meirin would go balistic.
In Maichinggu Machiko Sensei the eponymous character is occaisionally chased by animals who end up ripping her clothes off. This is in keeping with the fact that the entire universe in that series wants to see her naked.
Special A: Ryuu Tsuji; much to the anger of Megumi and Jun.
To Love Ru Darkness reveals that Lala's mom is the most beautiful woman in the universe — so much so that males of any species, including those that shouldn't find a humanlike form attractive at all, will be overcome by lust at the sight of her face unless she's wearing a special veil.

One Fables short-story plays this straight, another defies it. In the first story, a talking animal pretend to be a cursed prince who need to be kissed by a human woman for the curse to break. The truth is that the animal is really a manipulative pervert who simply enjoy being kissed by humans. The sob-story is just a trick to make them consent. In the second story, a human is actually a cursed talking animal, who need to be kissed by a female rabbit. However, he fail to find a rabbit who would kiss a human, they all just run away screaming.

In Mystery Men, the Spleen's leg is humped by a skunk.
In Transformers, even Mechanical Lifeforms from Outer Space want to hump Megan Fox's leg. She was amused. Sam wasn't amused.
In The Legend of the Titanic, one of the mice falls head over heels for Elizbeth.
In The Sword in the Stone, Arthur is (somewhat aggressively) chased by a Fiery Redhead squirrel.
- Justified, as he himself is in squirrel form at the time.

Fluttershy from My Little Pony Friendship Is Magic will often get exaggerated into this in Fanon. In the show proper, in "Swarm of the Century", a flock of parasprites got rather attached to Rainbow Dash... to be precise, to specific parts of her body.

Imprinting can cause animals (especially birds) raised by humans to ignore potential mates of their own species, and attempt to mate with humans instead.
Ah, Stephen Fry... even parrots love him.