A father and a son were painting pictures together, the son and father were drawing the exact same thing to a T and the son said “what happened to your hand?” looking at the scar tissue near the father’s knuckle, the father replied with “you know what happened, you were there.” the son continues to deny this until they both finish their paintings — they’re exactly the same.
The father passes out for a few hours and wakes up to find that there’s only one painting.