B.A.
My kitties did that when they were young. The first year, I had only one kitty, about 6 months old at the time. I'd come in after work to find her lying across the branches deep inside the tree. Year #2, I had the second kitty, and she was about 9 months old at the time. They would both take running leaps from the couch into the tree. I picked it up off the floor many times that year. For the next few years all they did was occasionally slap at an ornament.
Fast forward to this year - Smokey is 14 years old now. And guess what she's trying to do again - she's been attempting (and probably successfully while I'm not home) to lie in the branches. I've caught her a few times over the past couple days.