Blue jellyfish are very rare. They are known to be very agile and stealthy, and they create blue jelly instead of purple or pink like the normal jellyfish. In "Jellyfish Hunter," SpongeBob captures the only blue jellyfish in all of Jellyfish Fields and names him "Friend."
Role in series
SpongeBob tries to capture one at the start of the episode, but fails. Later, the same blue jellyfish follows SpongeBob to his house, captures him, and takes him to Mr. Krabs' factory. The blue jellyfish and SpongeBob stop Mr. Krabs from using the jellyfish SpongeBob captured for his own good and sets all the jellyfish free. The blue jellyfish then enters SpongeBob's net, and SpongeBob calls the blue jellyfish "Friend."
Friend can be seen among many other jellyfish.
SpongeBob's Atlantis SquarePantis
Blue jellyfish appear as one of many color variations of jellyfish.
So far, blue jellyfish are the only known jellyfish that can create blue jelly.
Blue jellyfish are likely one of the rarest breeds of jellyfish in Bikini Bottom and Jellyfish Fields.