When shit starts expanding in your intestines before it is ready to come out. The step right before prairie-dogging and two steps before the loaf is ready to be taken out of the oven.
Ted: Check out that girl over there...She's smiling at you. You should go talk to her.
Bill: No way! She looks like a yeastopotamus.
David Attenborough- famous Nat. Geo. narrator: "In the wilds of Africa, the only creature that scares the mighty cockodile is the equally large and ferocious yeastopotamus.