Tiny sex, type fucking, roleplaying etc.
This can take place in many styles and forms. From mild to extreme.

Examples:
[Removed] whispers, "Ember keeps right on playing with her tits, just as you say, the vixen grinding her hindquarters back against you. "Nnn... Fuck... I can't... keep this up..." she pants. "... Do you mind, umm... maybe peeing in me a little? In my butt, I mean? If you can manage it, I mean." to you.

[Removed] whispers, "Ember groans loudly as you saw that thick canine length in and out of her unlubed backdoor. "I -am- a slut..." she huffs, as she bends her forelegs, raising her ass in the air so that most that stream stays inside that freshly-stretched rear of hers. Enough of it flows back out, though, to dribble down her cunnylips and along the insides of her hindlegs, mussing up her fur with your piss. "... Nnn... Gods... I'm letting a stranger... Pee... inside my ass!" to you.

See also:
Cybersex
Nerds
IRC