"What Is This, a Crossover Episode?" is a catchphrase originated by the character Mr. Peanutbutter in the Netflix animated series 'BoJack Horseman.' Throughout the show, the overly optimistic Golden Retriever exclaims this line whenever he encounters the protagonist, BoJack, poking fun at the trope of television crossovers. On the internet, the meme is used to highlight any instance where two unrelated people, franchises, or subcultures interact in an unexpected way. It gained massive popularity on platforms like Reddit and Twitter as a reaction image for surprising collaborations, celebrity cameos, or even awkward real-life social encounters where different friend groups meet for the first time.