During her time at Hogwarts, Tonks would have a blast making herself look like Dumbledore for no reason, other than personal pleasure, and plopping down next to a random student and asking them the oddest questions, like
"Have you ironed your socks in the past week?"
Dumbledore realised eventually and joined in, so there sometimes were two Dumbledores' talking to the same student at once.
This became a habit and Dumbledore continued this, until the year he died.