a-higher-order
Explanation
The Joke
A man asks a woman, "Hey, do you like pickup lines about pickup lines?" She responds, "I've never heard one." He delivers: "I've never META girl who had." The next panel shows them in bed together, implying the line actually worked.
The Humor
The joke operates on multiple levels of self-reference ("meta" humor). The man's pickup line is itself a meta-pickup line -- a pickup line about pickup lines. The punchline "I've never META girl who had" works as a pun: "meta" sounds like "met a," so the sentence reads both as "I've never met a girl who had [heard a meta pickup line]" and as a reference to the concept of "meta" (self-referential) humor. The fact that this absurdly nerdy, self-referential line apparently succeeds romantically (as shown in the final bedroom panel) adds an additional layer of comedy, suggesting that extreme cleverness -- or perhaps extreme nerdiness -- can be attractive.