The girls like to tussle.
Especially in the winter, they get a little stir-crazy. In addition to climbing on every possible horizontal surface (and many improbable vertical ones) and knocking over arbitrary objects, the girls like to fight each other. If you did not know they were play fighting, you would think you were witnessing a kitty fight to the death.
But at the end of the day, they curl up together and sleep. This kitty bed is a one foot cube… Both kitties fit.