While the American military was developing the Bell P-59 Airacomet (one of the first ever jet planes), keeping everything about the experimental aircraft a secret was a top priority. They were so serious about this, that during development they stuck a giant wooden propeller onto the front of the craft make it look less suspicious. Why no one found the entirely chrome plane with a huge plank of wood glued to the front suspicious is a mystery for another day.
Though the idea of a plane without a propeller isn’t that unusual today, back when the P-59 was being developed, such a sight would have literally blown minds. So, just for a second imagine what went through the minds of the poor pilot who looked out of his window to see a plane with no propellers being flown by a gorilla in a bowler hat which saluted them before shooting off into the distance like a fart made of wet lightning.
In case you’re wondering, yes, that is something that actually happened. It’s rumored that the pilot behind the prank, Jack Woolams, did this to add yet another layer of secrecy to the project. As it was noted that any pilot who wanted to report an aircraft flying without a propeller would have also had to say that said aircraft was being flown by a gorilla. And come on, that almost never happens.