Swellbelly

Swellbellies are large blowfish enemies that dwell in the depths of Jolly Roger's Lagoon in Banjo-Tooie It reacts to threats by puffing itself up to an enormous size, piercing anything that gets too close with the sharp spines that cover its body.

Swellbellies can be easily defeated by using the Talon Torpedo or by firing Grenade Eggs at them in Sub-Aqua Egg Aiming mode.

Trivia

 * Swellbelly models resemble that of Puftup's from Donkey Kong 64 but is differently textured. The reason for this is likely due to the games' overlapping development period.