Grinny

Grinny is a dialectal American English term for a chipmunk.

a grinny face

That cheeky, grinny smile with those twinkly blue eyes

Reason thus, and if your heart beats till it hurts your ribs as a gray squirrel whisks across the dry leaves or a ‘grinny chipmunk’ waves you a derisive signal with his little flag from a log before your very nose, call yourself ‘fool,’ ‘idiot,’ anything that comes handy.