Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

The Joke

A woman says to a man (who appears to be reading from a document): "There are two types of people: those who like the Oxford comma, morons and pedants." The joke hinges entirely on the absence of an Oxford comma in her own statement. Without the Oxford comma (a comma before "and" in a list of three or more items), her sentence is grammatically ambiguous. It could mean either: (1) there are two types of people -- those who like the Oxford comma on one hand, and "morons and pedants" on the other (implying Oxford comma fans are morons and pedants), or (2) there are three types of people -- those who like the Oxford comma, morons, and pedants -- but the missing comma collapses the list into apparent apposition.

The brilliance is that the statement is self-demonstrating. By omitting the Oxford comma while complaining about people who care about the Oxford comma, the speaker inadvertently creates exactly the kind of ambiguity that Oxford comma advocates warn about. Her sentence accidentally (or deliberately, depending on interpretation) equates Oxford comma enthusiasts with "morons and pedants."

The Humor

This is a precision-engineered grammar joke. The entire comic is a single panel because the joke needs nothing more -- the sentence itself does all the work. It delights grammar enthusiasts because it is a perfect self-referential demonstration of why the Oxford comma matters. Regardless of which side of the debate the speaker is on, the sentence undermines her position through its own structure. Anti-Oxford-comma people will read it as calling comma fans "morons and pedants," while pro-Oxford-comma people will point to it as proof that omitting the comma creates confusion. The joke works for both camps simultaneously, which is a rare achievement.

References

The Oxford comma (also called the serial comma or Harvard comma) is the comma placed before the coordinating conjunction in a list of three or more items (e.g., "red, white, and blue" vs. "red, white and blue"). It is one of the most passionately debated points in English punctuation, with style guides split on the matter: the Oxford University Press and the Chicago Manual of Style recommend it, while the Associated Press Stylebook generally omits it.