Uterus or GTFO!
“I don't actually have anything against uteruses, I used to live in one, for a time. Then I sort of grew out of it like that Blue T-shirt with Thomas the Tank on it that I used to like. Anyway, it's vaginas that are yucky”
Uterus or GTFO! is a common phrase used in IRC for when a person desperately needs a fap, and the normal "Tits or GTFO!" doesn't help. If a person is unable to immediately provide a link to an image of preggo pron within thirty seconds, they are immediately banned by the chanop who called it. This, along with the fact that most people don't know where to look for uterus porn, accounts for the low population of #asciipron on Freenode. This sudden bannination and its effects are collectively known as The Uterus or GTFO! Theory. Uterus or GTFO! is generally declared porn emergency 3, in that one wants weird pornography but not so much so that they resort to porn emergency 4.
The phrase "Uterus or GTFO!" is derived from three phrases. "uterus" denotes that the user wants to see a uterus, but also implies that they want to see a fetus growing inside said uterus. A picture of a nonpregnant woman who has a uterus isn't enough- many noobs have been banned for that mistake. Also, diagrams or medical drawings of a uterus (even one containing a fetus) generally isn't enough either: its best go with a semi-naked or fully naked pregnant female. "Or" implies a threat, while "GTFO" is the actual threat- failure to comply can result in you getting kicked, or banned. The Internet is indeed serious business.
The answer is simple. Women with huge bellies with something moving around inside said huge belly is HOT! Well, at least to most heterosexual males. Why, exactly, this is is something that the psychology community has yet to piece together a reasonable explanation for. Its extreme improbability is a mystery that nobody has cracked yet. Maybe it has something to do with Rule 34.
What to do when asked
Something to keep in mind at all times when someone tells you "Uterus or GTFO" is that they have been driven stark raving mad by the idea of preggo porn. YOU MUST send them a link to preggo porn immediately if this happens! If the above image doesn't placate them, you must secretly take pictures of your reasonably attractive pregnant female relatives, or, even worse, browse wikipedia for pictures. If all else fails, you can even try 4chan, though you can't blame us if you leave the site in a different mental state than when you entered it.