When I was younger, we had a guinea pig named Snowy (which was odd that we named her that, since she was mostly brown with white markings xD We were kids, and liked the name) who was excellent at getting out of her cage. We kept her in the playroom that my sister and I shared, and we always tried to close the door when we left the room just because we knew that no matter what we did, she would somehow get out and be scurrying around whenever we came back into the room. One time, we left the door open while we went to school. When we came back, we realized our mistake and rushed to the room. My cat was standing guard over the guinea pig, keeping her from escaping! The cat didn't hurt Snowy or anything, just stood there making sure she didn't get near the door. It was pretty funny, and our cat got major pets and cuddles as a reward