In Germany when someone needs a fake/example name for a demonstration of something it is usually "Max Musterman", you'll see it in ads for things, demos where people are meant to be typing their name in somewhere, etc ect. It's a cute in-joke because "Muster" means "template" or "sample" which ofc is funny because the name itself is an example and not a real person.
I think it's charming that we've collectively chosen and adopted this across the board and it made me wonder if any other countries have something similar, I can't say I've noticed one in the US.