We had a visitor recently. The four legged variety. I opened the door to go outside one evening to find him clinging to the outer door at about eye level. I called the boys over so they could get a good look at him.
Yep, we had a frog on our door. It was about the size of my thumb. Our outer door is a little warped and doesn't close securely, so it was easy enough for him to get inside. Whether he'd find his way back out, however, was a question, so I nudged him to the outside of the door so he would hopefully find his way back home.