Marty Moussa appears in The Santa in the Slush.
His wallet was pick-pocketed by Jeff Mantell on Christmas. This prevented him and his family celebrating Christmas that year. He found Mr. Kringle outside a box store and punched him in the nose. The people around him begun staring at him - fearing he was a terrorist - and he fled.
Later, he is questioned by Booth as to whether he killed Mr. Kringle. Booth later returned Marty's stolen money.