I've noticed the past few days my 8 month old male kitten stalks my 15 yr old female cat when the cat uses one of the two litterboxes. He either gets on top of it or sits outside the closet in an attack mode. When she gets out she has to run for her life as he jumps her, they do the roll into a ball pawwing each other, no claws til shes had enough, and she hisses. Thats when i usually get involved like the mean daddy i am walking like frankenstein towards him with my arms spread out , haha one foot at a time til he crouches into a ball and rolls over. He is so funny, and the cat and kitten get along great, but he just has 1000% more energy than she does and i dont like her getting stressed out being older than 15.