Assuming there's no magic stuff going on, the chicken's probably just tensing his muscles using some bit of alien technology. (Evidenced by how his hands are grasped shut and the tightened pose his arms are in, like he's banging on his desk or something.)
Him not being able to move is probably because he's trying to weaken that tension, (Which is what you'd do if you wanted to stand up from that position.) which just gets normalized nearly instantly. Instead, he should treat this paralysis like a sort of Chinese finger trap and tighten his muscles more instead and try and roll himself out of the chair.
But this guy's stupid, so he's definitely not going to think of any of that.