Monster's Ink
The act of masterbating in the middle of the night whilst your partner is sleeping. Then on the brink of ejactulation, you let out a horrify shriek while unloading on the their face.
"Dude, last night I totally pulled a monster's ink on my chick! She woke up screaming!"
Monsters Inked
When a rather grizzly and sweaty gay man bursts through your closet door at night and ejaculates into your room, then disappearing back into the closet, never to be seen again.
I though it was a nightmare but in the morning I realized I was just monsters inked.