Whenever someone opens the door to the garage, Phoebe ALWAYS goes into the garage, so when the big door is open, you have make sure you shut the door so she doesn't go outside. One time Phoebe got into the garage while we were doing something, and we shut the door. By the time we figured out that she was out there, she had been in there somewhere around 45 min! Luckly it wasn't hot or anything.
Both kitties love to explore the closets, and I can't even begin to count how many times Phoebe (and Cleo, just not as often) have been shut in there.