Paint the canvas

To succeed in leaving fecal residue on the toilet bowl after a flush.

Be right back, I'm gonna go paint the canvas.

Jacobean chair leg

Originating from South London, the term is used to describe a taking dump so massive that it resembles an old English style of furniture, characterized by ornately carved chair legs and a dark finish.

Friend: "Mate, what took you so long?"
Guy: "Sorry, had to carve out a Jacobean chair leg."