Wolfgang shakes their head so hard their hair breaks free of the elastic that had been holding it and goes flying around their face, falling in front of their eyes. That goes a way towards hiding their red face and their expression, which, underneath their hair, is clearly not upset, but embarrassed. He wasn't supposed to see this, no one is supposed to see — they're supposed to believe this happens with incantations and potions. Even the Doctor uses an ancient old grimoire bound in human skin, full of thousands of years' worth of arcane rituals. Wolfgang plays with dolls.
It occurs to them that they can't hide this from him. Eventually, he's going to see it. It's innocuous but embarrassing now, but next time — there's a darkness there. It's not always pretty.