I had sex with this girl I'd met at a party in a friend's house and we'd smoked weed together and made out and passed out in a guest room in each other's arms, while watching Arrested Development. The next morning, we had sex. We were both half-clothed, naked from the waist down. Towards the end of it, I grabbed a hold of her ass and started jiggling it up and down and back and forth. This made her cum, like intensely. I know because she craned her head up to the ceiling and started making these extremely high-pitched moans and then said, "I'm about to cum!" This made me jiggle her ass harder and slide a hand further down, until it brushed up against the point where my dick met her pussy. And then, as this was happening, my friend, who is 28 years old and had apparently just woken up and either didn't hear us or didn't care, barged in to the room just as we were both actually climaxing and said, "Hey douchebag, let's go get some break--" Then he saw me lying backwards on the bed and her head cocked back so she was looking at him almost upside down. She shrieked as he spoke--I think first it was an orgasm shriek, then it turned in to a what-the-fuck skriek. My friend immediately changed his response to; "Yeeeeaaahh, the little tyke it getting it done!" And slammed the door.
We all still went out to breakfast together. It was super awkward. Morals of the story: jiggling her ass works, and people walking in aren't necessarily deterrents.