My beloved mice, Sputnik and Magic, now at RB, used to do a funny and unique trick. They climbed to the top of their little 'house' in their cage, and they would jump up and sort of 'backflip' and grab the bars on the top of the cage and 'walk' with all four paws. And they would do all this upside-down clinging to the top of the cage! As my 6-year old brother put it, they were Spider-man Mice. Has anyone else seen this before? Does anyone know why they would do this?