Shawn: Halloween at Dusk...
Either Shawn was being completely paranoid, or this Leonard was a good actor. But getting screamed at by Junior's mom had rattled him, and he wanted either proof he was right or reassurance he was wrong before he could go out trick or treating. So he kept his tone playful, so that if this was all a misunderstanding he could pretend it was all just a game.
"Well, maybe you aren't Leonard at all! Maybe you're a robot in disguise trying to trick me!" Shawn gave Leonard a silly grin, but he was paying close attention to his answer. "I'll ask you something only the real Leonard would know! Like, how did we first meet?"