Knockin on cotton

When you gotta poop right away. Because your poop is touching your cotton under wear.

Hey man; I gotta go take a shit right now! It's knockin on cotton!!

Shit cast

Shit that's dries on your pens after having anal dex.

First time I had anal sex. I got a shit cast.

Sheit cast

Feces that covers and dries on your penis after anal sex

I always get a sheit cast after I have sex with my girlfriend.