A childhood belief about general

My hamster, Charlie, had this annoying habit of running up the chimney when we let him out. I remember all the hours I spent with my family staring up the chimney, watching for any rodent-like movements. Anyway, each time he came down, he would be covered in soot. Since he had gone up a white hamster, and come down a black one, I reasoned that it was in fact a different hamster that came down each time. I thought there was this whole city of hamsters living in our chimney, and whenever one wanted to rejoin his family, he would go up the chimney and another one would be sent down. I think I must have had an overactive imagination.