Ron actually fell through the window once. He was laying on the window sill (sp?), and next thing you know, he was outside in the bushes. He actually broke our screen! We weren't looking at the time of the accident, but I am assuming he forgot in his sleep where he was and tried to roll over. Luckily, we live in a one story house. If I had a 2nd story, I wouldn't allow my cats to sit in the window.