King Calamari is a giant Bloober, and a minor boss encountered in Super Mario RPG: Legend of the Seven Stars. It sank Jonathan Jones' ship (as chronicled in various logs found throughout the vessel) and was locked in the Treasure Room. Mario has to work out a six-letter word before he can enter the Treasure Room using clues provided in various rooms of the ship. After Mario learns the word is "pearls", King Calamari allows him in the Treasure Room to battle.
After defeating King Calamari, Mario and his allies gain access to the lower section of the Sunken Ship.
When the battle starts, the player encounters three tentacles in each of the first two sequences; the tentacles attack by either slamming a party member or throwing one high into the air. The latter attack does not reduce a party member's HP, but it induces the Fear status effect regardless of immunity. The last sequence is fought against King Calamari's main body and two other tentacles. Even if King Calamari is defeated, the remaining tentacles need to be destroyed to finish the battle.
King Calamari's name is from calamari, a term for edible, fried squids. "Calamari" is also the word for squid in Greek and Italian; in Spanish, the word for squid is similar, "calamar." However, King Calamari was most likely named directly after the food term.
In the Japanese version of the game, the password to get to King Calamari is「すいぞくかん」(suizokukan), which translates to "aquarium" rather than "pearls."
The "tentacles" appear to actually be arms, as the suction cups travel all the way up, as opposed to simply being on the end.