correlation-chains
Explanation
The Joke
The comic is titled "Funtime Activity: Correlation Chains" and presents a series of graphs showing correlations: happiness correlates with amount of sex, income correlates with happiness, likelihood of owning a signed Harry Potter novel correlates with income, and likelihood that you are in fact J.K. Rowling correlates with the number of your possessions that J.K. Rowling has touched. The "result" at the bottom shows a man excitedly asking a woman to come home with him, claiming he wants to "have what happens with Hermione's kids" -- essentially using this absurd chain of correlations to proposition her.
The Humor
The comedy works on multiple levels. First, it satirizes the common logical fallacy of chaining correlations together to reach an absurd conclusion. Each individual correlation might have some basis in data (more sex correlates with happiness, higher income correlates with happiness), but stringing them together leads to the nonsensical conclusion that having sex will somehow make you J.K. Rowling. Second, the punchline shows someone actually trying to use this ridiculous chain of logic as a pickup line, asking someone to come home so they can "have what happens with Hermione's kids" -- a hilariously convoluted and unsexy way to proposition someone while simultaneously revealing they are a Harry Potter nerd. The woman's surprised "Really?" suggests this terrible approach might somehow be working.
References
The comic references the well-known statistical principle that "correlation does not imply causation," and further extends it to show that chaining correlations together compounds the error. J.K. Rowling is the author of the Harry Potter series, and Hermione Granger is one of its main characters.