Most flight attendants are well used to answering silly questions from passengers who, in different circumstances, would probably cringe at their stupidity. There's something about the exhaustion and stress of air travel, or maybe just the poor quality of the air on board, that brings out the eejit in the travelling public. But the cabin staff manage to smile and explain the obvious with professional courtesy. Almost always.
Occasionally the request is so daft that they can't help but rise to the bait. This happened to one flight attendant when, just after the safety briefing had identified the exit signs, a passenger called her over and asked if the signs mounted on the cabin's ceiling indicated another exit through the roof. "Oh yes," replied the bemused stewardess, "That's right, it's the exit for good jumpers. We even keep a small trampoline to help people to jump up and out of it." Fortunately the flight arrived safely and the enquirer didn't need to use his new found knowledge.