A man is going down on his girlfriend. He's doing his best, but she keeps yelling "Harder, more, fill me up!" So he puts in one finger, then two, then his whole hand. Now he's up to his shoulder in her, being engulfed, and she's still saying "Fill me! Fill me!"
So he puts his head in, then his whole torso, and soon he's all the way inside and realizes he can't find the way out. He takes his flashlight - because of course he has a flashlight - and starts looking around before he trips and drops it.
Now he's fumbling about in the dark, desperate to find the exit, when he feels something weird.
"Hey! Watch it!" says the weird thing.
"Oh man, are you stuck in here too?" he says. "Help me find my flashlight and we can get out of here."
"Flashlight?" says the other man. "Hell, help me find my keys and we can drive out."