Steven is just laughing softly in response to the hair-mussing when he question catches him off guard. He blinks, and then looks at her, and her hand, and the way it's angled, and...

"I thought my pants fit weird!" he says, sounding shocked. He stretches out his legs, showing how his pants are sitting further up his leg than normal. "Oh no. I meant to quit doing the growth stuff, but maybe I didn't go back to the right size after all..."

He's phrasing this as a bad thing, somehow.