While in the middle of pooping her shorts, Twi got startled and turned around.

I initially was going for a new style of messing edit that would be show-accurate (similar to the new style of wetting), but I couldn't get it exactly right so I went with the onomatopoeia again. (Besides, often in cartoons when a character soils himself/herself — provided it's the kind of show that would do such a thing, of course — it doesn't even show anything except a smell. Not that I don't like edits that would say otherwise, of course)