The Flatterchuck is an enemy in the Pikmin series that appear in Hey! Pikmin. It acts more like a platform than an enemy.
The Flatterchuck lies flat on the ground until Pikmin or Captain Olimar walk onto it. When that happen, it will launch its body upwards to get rid of them, sending anything standing on it up into the air. The Flatterchuck is a pasive enemy and will never try to attack Pikmin or Olimar.
Hey! Pikmin log
"It sleeps flat, blending in with the ground, and will only move if something walks across its back. At this stimulus, it leaps high into the air. It's difficult to say who's to blame when this happens—the Flatterchuck itself or the one who stepped on it."