Does anyone have any good ideas for stuff to use in Knickerfilling? (Putting dirty foods into your underwear). I've tried whipped cream, chocolate sauce, bananas, purd bananas, pudding, even oatmeal. Trying to find some new stuff to use! Thanks!

cottage cheese...not fond of the smell but i've often wondered what it would look like, or, how the girl would react...

Beans. Slimy messy canned "baked" beans.

Partially melted ice cream.

Greasy gravy.

Eggs.

Not tried but possibly: Applesauce, creamed corn, mashed potatoes.

Nacho cheese sauce or grape jelly

Obviously, custard is a big favorite!
Frosting, cake batter, treacle, yoghurt, jelly, trifle are all good sweet choices.

Savory items can get a bit smelly and gross but the textures can be fantastic!
Try baked beans, spaghetti hoops/short cut spaghetti in sauce, thick tomato soup/sauce, mayonnaise, ketchup, thick gravy.
I just try to avoid anything spicy that might sting...