Octo

Octo, originally known as Scowler or the Squid, is a big squid that first appeared as one of the bosses in Wario Land 3.

Wario Land 3
In Wario Land 3, Scowler is the boss found in Sea Turtle Rocks. His main attack is to try to grab Wario. If he does, Wario will be thrown out of the cave. At the first time, his weak spot is on his head, Wario has to touch it which will damage the creature. Then, the weak spot will move to his underside. He sometimes attacks with ink to turn the water black and obscure vision, leaving only his head visible. Upon defeat, he leaves a ring behind which helps Wario access the Gray Chest which contains the third of the five music boxes.

Dr. Mario 64
Scowler, now renamed Octo, reappears in Dr. Mario 64 as one of the enemies Dr. Mario or Wario have to face.

Unlike in his original appearance, Octo's body is colored orange rather than black in the American release of the game. In the later port of the game released in Japan as part of Nintendo Puzzle Collection, he retains his original black color scheme. His appearance may have been changed in Dr. Mario 64 due to a possible resemblance to blackface actors, similar to another situation faced by Nintendo with one of its Pokémon, Jynx.

Trivia

 * On the back cover of Chinese version for Dr. Mario 64, Octo, along with Spearhead, Appleby and Hammer-Bot, were referred as Mad Scienstein's minions.