After giving you a nice view of the back of her clean white panties, Donna starts to wet herself a little. But that's only a sign of things to come.
Several short farts announce the true payload, a blatant panty-shit which has Donna's undies turning lurid poop-brown.
She takes delight in showing you her lumpy bulge from the back and the front, crouching down and even giving the contents of her panties a squelchy squidge through the back of her panties.