Oh my. I'm just imagining the mayhem that would ensue should a squirrel ever shove his way in through our doggie door. I usually lock ours at night so we don't have to worry about visits from the nocturnal creatures of the forest (or the dogs heading outside in the dark to tangle with one of them) but I've never considered that something would come in during the day. Yikes! Glad your visitor didn't stay long & cause too much mischief.