I saw a video once of a prank where two girls go up to a stranger asking them to take a picture of them across the street. The stranger takes the photo and when the two girls start crossing over to the other side, a car passes by and the two girls are replaced with two old men wearing the same shirts. Even the Polaroid photo shows the old men. It's genuinely funny and completely harmless. It just makes the person getting pranked go, "Wait, what the fuck???"

I do hope the people were told that they were pranked though and that they don't live the rest of their lives thinking they're insane 😂

ETA: also this video where the guy puts on the collar and leash of his blind husband's service dog when he asks him to go get his watch. (He immediately reveals himself when the blind husband gets back to pick up his service dog's leash again and the husband thinks it's hysterical).