I used to hate facial hair.

This zinger is a masterclass in wordplay, relying on a pun that is both literal and figurative at the same time. The humor clicks when you realize the phrase "it grew on me" has two distinct meanings that both fit the setup perfectly. The first is the common idiom for learning to like something over time. The second, more literal meaning is that hair physically grew on the speaker's face. The punchline's genius is that it uses the literal action to explain the change in opinion, creating a delightful and groan-worthy moment of clarity.

The joke also lands because it's so relatable. Trends in facial hair are constantly changing, and many people who decide to grow a beard or mustache go through a period of uncertainty. They might dislike the initial scruffy phase or be unsure if the look suits them, only to eventually embrace it. This one-liner cleverly captures that entire emotional journey and connects it to the simple, physical act of growing hair, making it a perfectly crafted, economical piece of comedy.