Normally the lemur would rise and lean into such affection, but in this instance he doesn't. Perhaps it is the trauma of having been kept in captivity in this foreign place for however long, or perhaps he's just reacting to the unconscious body language that Aang is displaying.

"It's okay, buddy. He's a friend."
Who, exactly, are you trying to convince here, Aang?
Momo's tail wraps around the boy's neck protectively.

The Vendor takes this opportunity to slip away, and Aang's eyes track him as he makes his exit.

"We should probably go."