The phrase in question refers to a riddle, often posed as a joke, playing on simple arithmetic and common associations. The punchline typically relies on a series of flawed calculations intended to “prove” that fire trucks are red because they have wheels and grass is green, among other tenuously linked elements.
The humor of this wordplay lies in its illogical structure and the unexpected, absurd conclusion. Its value exists primarily as a lighthearted form of entertainment, often used to engage children or as a quick icebreaker in social situations. Historically, these types of jokes reflect a fascination with language and the manipulation of logic for comedic effect.