Not long ago, perhaps in the mid-1990’s, a young Japanese girl had a vision… (This link is safe.) I have no idea if this is legitimate — the person he references only has one hit on Google, and it’s at this site.

These may already exist, but I was not able to find them with Google (perhaps that itself means it doesn’t exist).

Interior pet door - Great for people who have pets that sleep with them, and still want their privacy. It would be installed by carefully cutting a rectangular hole on the opposite side from the [...]