"I can pa--," he tried to say, showing him his money. But he was cut off by the suddenly jovial stranger. Was this a trick?
He smiled sheepishly at the burger stand cashier as the guy shrugged.
"Uh, thank y-" he got out before the guy beside him spoke up again. His eyes widened as he was jolted by the patting, having to regain his balance at the enthusiasm the 'friendly gesture' included. He might have even uttered an unsuspecting "Unf!" in surprise.
"Heh, shiny," he said uncertainly, rubbing his shoulder.