The sentence that uses humor in the excerpt is:
"Wall, sir," sed I, "you's never more mistaken in your life. You hain't gut a orfiss I'd take under no circumstances. I'm A. Ward. Wax figgers is my perfeshun. I'm the father of Twins, and they look like me--BOTH OF THEM."
This sentence employs humor through the playful assertion about having twins that look alike, emphasizing the absurdity of the situation and the identity of the speaker.