The turtle is peeking
When you have to take a crap so bad that it feels like it has already started to "peek" out your ass similar to a turtles head when it comes out of its shell.
The turtle is peeking. If I don't get to a bathroom right now, I'm going to shit my pants.
Turtle Peeking
A euphemistic expression regarding the extreme urgency to defecate and holding it in as much in as possible. Having the pressure of a fecal turd poking itself partially out of the bum hole while trying to make it to the closest restroom.
Roger sprinted down the hall from his desk to the restroom. He has a turtle peeking.