mack the knife
Sneaking up on your partner while they're asleep and sticking your penis in their butt without them knowing. It's like a surprise attack in the middle of the night.
"I macked the knife at 2 a. m. and my partner didn't even wake up.", @NightAttackKing
"He did it so fast, I didn't even know what happened until I woke up.", @SleepySoul
"Macking the knife is the best way to start your day. Or your partner's.", @MorningSurprise