Riddles Posed By The Internet Only Real Einsteins Can Answer

Voting Rules
Vote up the riddles that left you scratching your head.

"We make your brain cells work overtime, but we're also lots of fun. What are we?" Really hard riddles, of course - and ones much more difficult to figure out than that opening line.

In case you've missed the puzzling phenomenon, riddle memes that ask questions most people can't solve will keep you going for days, either scratching your head trying to find the answer, or patting yourself on the back for being so darn smart.

Whether you try to solve the world's hardest riddles with or without peeking at the solutions, you get an "E" for effort just for trying. Or an "E" for Einstein if you know all the answers...