Similar to the sudden werewolf, but can be done on any night. During doggystyle, right before climax, bite your partner on the neck. When he/she whips around and asks, "WTF?!", shoot your man-milk right in their eyes (it'll sting like garlic). When they search blindly for a weapon, turn into a bat and get the hell out of there, Bela. Be home before sunrise.
Kristina had been giving me a hard time lately, so I decided a sneaky vampire was in order. Bitch tried to put a stake thru my heart.