bachelor-cake
Explanation
The Joke
The comic shows a woman bursting out of a large tiered cake -- the classic bachelor party trope -- but instead of a stripper or exotic dancer, she is a sociologist. She enthusiastically declares: "Did you know that the connection between food and sex is highly cross-cultural?" The caption reads: "For the bachelor party, we hired a sociologist to burst out of a cake."
The joke takes the well-known bachelor party cliche of a woman jumping out of a cake (typically as a sexualized performance) and replaces the expected titillation with dry academic commentary. The sociologist is performing the same physical act -- emerging from a cake at a party -- but delivering a lecture on the anthropological relationship between food and sex rather than anything provocative.
The Humor
The humor comes from the massive gap between expectation and delivery. The visual setup (woman in a cake at a bachelor party) triggers a very specific cultural expectation, which is then completely deflated by the academic content. The sociologist's factoid about food and sex is technically relevant to the situation -- she is, after all, literally inside food at an event connected to sex and marriage -- but the delivery is so clinical and professorial that it becomes the opposite of titillating. It also plays on the SMBC-recurring theme of academics being socially oblivious, treating every situation as an opportunity for a lecture, even one that is supposed to be entertainment.