My indoor cats don't go outside, but I have an incredibly friendly neighborhood feral that I also take care of. He's (well, formerly "he") been living on my enclosed porch for a few weeks, one of the unfriendly local feral cats tore a big hole in his leg that required stitches. I'm not letting him out to roam until it's healed. The silly bugger thinks everyone and everything is his friend, he keeps trying to make friends with my cranky old female indoor cat, and when she hisses at him, he just gets a really confused look on his face.