Yorkshire Canvas

The act of inserting a whole packet of crayons into your sphincter, then once ready to defecate, you excrete the contents of your rectal passage into the toilet bowl. Thus resulting in an extravagant display of colours

Dude 1:Dude, I totally made the most impressive Yorkshire Canvas the other day.
Dude 2: Dude, sweet

Dude 1: Dude, totally