When Team Avatar planned on visiting the Southern Air Temple, AvatarAang claimed that there was a prickle snake in Sokka's sleeping bag in order to wake him up and used a stick to mimic the sensation. The thought of the animal caused Sokka to awaken in an instant and scream in terror.[1]
While camping in some areas of the real world, especially outside of a tent, creatures such as snakes can hide inside sleeping bags, posing a danger to any human occupants.