One classic Far Side strip has a scientist coming to a bad end when he uses his time machine to take a large rectal thermometer back to the Age of Dinosaurs to conduct some tests...
Reminds me of the original Star Trek episode where an Earth ship visiting a distant planet left behind a book about the Chicago Mobs of the 20's, and when the Enterprise arrived years later, the natives had modeled their entire society on it.
H.G. Wells' short story "The Man Who Could Work Miracles" ends with this happening, thanks to a very ill-advised wish on the protagonist's part. Also the 30's movie adaptation...
The "original book" was written co-currently with the movie. The book/movie combo was loosely inspired by an earlier short story by Clarke called The Sentinel.EDIT: I was trying to reply to dnc's comment
Additionally, I've read that the original version of that critter didn't have that headpiece; it was added after the female star of the movie made fun of this squatty little thing trying to be scary.
"And even if he was a lazy man - and The Dude was most certainly that - quite possibly the laziest in Los Angeles County .. which would place him high in the runnin' for laziest worldwide."