Chester does this thing, a deep growling rumble, when he plays. His paws stretch forward head dips shoulders crouch, rounding up on hind legs, tail nodding to the left, a sideways bob bob bob, a bow thumping his rump to a number.
Visitors don't know whether to laugh and stretch their hands for his puffy fluff, or stand fixed like a tree. (Though if he takes you for a tree, that could be another problem.)
He isn't angry; He just takes his games very seriously-- even the silliest ones, the yellow ducky tug of war he knows he will lose, the crushed-liter-bottle-hide-'n'-seek that leaves him treatless-- You need to take them seriously, too, for Pete's sake. And just to remind you that this play is business, people, he growls: Play, doggone you, PLAY!