From the Super Mario Wiki
Bobbin' Squeeklies are the largest species of Squeeklies that appear in the game Donkey Kong Country Returns and Donkey Kong Country Returns 3D. They only appear in the level Crowded Cavern, which features various types of bats attacking Donkey and Diddy Kong.
At the beginning of the level, the Kongs find a Rocket Barrel which they need to use to progress through the level. the rocket, however, causes a very loud noise that awakens the entire Squeekly Family from their sleep. Because of this, the leader of the Squeeklies, the Big Squeekly, starts to angrily chase the Kongs throughout the level.
Several of these large, blue Squeeklies appear in the stage. Bobbin' Squeeklies attack the Kongs by bobbing up and down, attempting to get in the Kongs' way. If one of the Bobbin' Squeeklies hits the Kongs, the primates lose one heart and the Squeekly is defeated.