Fistface Wembley

I love how flexible the Wembley puppets' faces are. They give him such a great range of expression. However, there's one expression he often pulls, where he opens his mouth and sticks his nose into his lower jaw, that I just can't figure out. What the hell is this supposed to be? A grimace? A scowl? Bafflement? Facial grand mal?

Will move to scrapbook when I figure this out.