I went to visit a good friend at her apartment building in Portland in 1990. While climbing the stairs to her floor, a little mouse, was sitting on a step. I was sure it'd run off as I got closer. I reached that step and the little mouse moved toward my foot. I put my hand down near it and it crawled right into my hand.
I took it into my friends apartment. She grabbed a box, but didn't want to interact with my new friend. I knew that he must have been someone's pet, because he had no fear of people. I took him home, made him a temporary home in a bucket, and she put up a notice in her building. Nobody answered the notice, so I bought a proper cage. Had that little guy for about 2 years.
Named him Machismo, after a local Mexcan fast food chain named Machismo Mouse.