Calvin's mother bursts into the bathroom another time, now Kevin stands at the toilet and pees - his front is covered by a wall, but his bottom is partially exposed under his shirt, plus his bottom is briefly seen again when he pulls his pants up.
A bunch of kids nude at the beach. They pee into a water-filled pit in the sand. One of them asks a chubby teenager to help them retrieve a beach ball from the pit. Then he kicks the teenager's butt, and the teenager falls into the pit. Full frontal nudity of several of the boys peeing in the pit.