Leonard: If Penny didn't know that Leslie had already turned me down then that would unambiguously mean that she, Penny, thought I should ask her, Leslie, out, indicating that she, Penny, had no interest in me asking her, Penny, out but because she did know that I had asked Leslie out and that she, Leslie, had turned me down then she, Penny, could be offering me consolation. "That's too bad, you would have made a cute couple" but while thinking "good, Leonard remains available."
Sheldon: You're a lucky man Leonard.
Leonard: How so?
Sheldon: You're talking to one of three men in the western hemisphere capable of following that train of thought.
Leonard: Well, what do you think?
Sheldon: I said I could follow it, I didn't say I cared.