Ulrika and Unwin the Untidy Twins
Gloria Eveleigh, author
Ulrika and Unwin never put their toys away when they've finished playing with them. They hide them under the bed or pile them up on the floor. Their cousin, Umber, comes to stay and ends up tripping over some toys and bumping her head. The twins are very shocked at this but learn that toys left around not only look untidy but can be dangerous as well. After that, they never leave their toys around again.