Grubby Groo is a character on the KaBlam! short The Off-Beats. He is the adult friend to the Off-Beats and looks like a beatnik. He is the only adult that knows The Populars are just mean kids, despite their "nice act" when he walks by them. In the episode "The Sprain", he gave Betty Anne Bongo a Junkyard Sundae and in "Your Shoe's Untied" (Shoelaces), he tied Repunzil's shoes. He is voiced by The Off-Beats series creator, Mo Willems.