Messy Pigeon

Standing up on the toilet lid and doing 1,s and 2's, usually they do not go in the toilet.
The whole area, including the walls, floor and the toilet itself should be covered in waste so it is advisable thtat you don't do it in your own home.
It is often done on purpose to get back at someone.

"That Kane was sporking your girlfriend".
"That Justin Bieber! I am so going to do the biggest Messy Pigeon the world has ever seen at his place!"