Muddy Duckskin
When you fuck a girl in the ass so balls deep, that her shit gets all over your scrotum. You don't notice the wet shit on your sack until you look down. It's quite shocking.
Unlucky Dude: What the quack, Kacie? Your mud is all over my hairy ballsack!

Kacie: It's your own damn fault for penetrating my asshole so gosh darn deep!

Unlucky Dude: Well now I have a Muddy Duckskin...thanks a lot!!!!