He's visibly startled by Linda, but only for a moment. Chouji breaks into a smile at her greeting and returns the wave. "Hello, Linda!" And the comparison to Kiba is apt enough with Linda's current position, considering how long their friend carried Akamaru on top of his head.

"More like a nin dog or more like a summons?" Chouji asks for clarification, given her sudden appearance. He has no idea what a Pokemon is, of course.