"I’m my own grandpaw", baby
The cover of this sheet music for the 1947 novelty song "I’m my own grandpaw", written by Dwight Latham and Moe Jaffe, contains an old man / baby reversible optical illusion.
"I’m my own grandpaw", old man
The song explains the riddle of how a man can be his own grandfather. It’s an old puzzle:
A proof that a man may be his own Grandfather.There was a widow and her daughter-in-law, and a man and his son. The widow married the son, and the daughter the old man; the widow was, therefore, mother to her husband’s father, consequently grandmother to her own husband. They had a son, to whom she was great-grandmother; now, as the son of a great-grandmother must be either a grandfather or great-uncle, this boy was therefore his own grandfather.
I gather that it all makes some sort of logical sense… though not to me. I’m the one who’s always nodding knowingly at family gatherings when unknown relatives are introduced, because I get confused with any relations beyond my immediate family.
The Muppets sang about this, which makes it funnier, though not any clearer to me.
I’m my own grandpa