Big Lenny

Big Lenny is a large and dangerous Jellyfish, and one of the only known Jellyfish to actua

Dr. Manowar, the only person to survive an attack from Big Lenny

lly kill it's stinging victims. As SpongeBob revealed in I'm Your Biggest Fanatic, Dr. Manowar is the only person who has survived an attack by Big Lenny, getting by only with a huge bump that hurts when touched. This implies that Big Lenny has stung, and thus killed, numerous other Jellyfishing enthusiasts.

Trivia

Big Lenny has never made a true appearance in the series.
Unlike other Jellyfish stings, people can die if stung by Big Lenny.
It has never been seen in places like Jellyfish Fields, so it probably lives in a prison or a safekeeping area.
The only time it was seen in Jellyfish Fields is in the game Operation Krabby Patty.
He may be a Portuguese Man-of-war or an Australian Box Jelly or even a Lion's mane, because all are incredibly deadly.