Boone reacts with a smile to fairly vigorous thumping by Gunner, doesn't like when it stops

Glad to see Boone and Gunner having a moment. Wonder why Boone likes the thumping. Any ideas?

The evil eye of Ma Bus returns as she constantly tries to cover or spread Boone's hand as she flips the screen. The wrist in the foreground of the last photo is on his right hand. You can tell the screen is flipped by looking at her wedding ring finger.