He only can say Boop. He would never say a word except boop because he doesn't want his teammates to know he really cares or talks. He understands english but doesn't speak it. Instead, he speaks by saying "Boop." Boop Bunklebee is a perpetual grump. On the outside, he's a bundle of negativity and indifference. On the inside, he cares deeply about the work that he and his teammates do. Boop's external persona masks a persistent fear of failure.