I like We Bare Bears because it's just funny!!!!
Anyway Grizz is a Grizzly bear (everyone knows that).
He acts as and is seen as the leader to his two brothers. Out of the three bears, he stands out the most and sets good examples for them. He's almost always optimistic and gluttonous. He loves to make friends, enjoying attention and generally being very social and friendly.
That is from the fandom wikia, I don't know so much.
He's a happy bear.