I used to hate facial hair, but now it's starting to grow on me.

Behind the Groan

When an Opinion Grows Literally

Something that “grows on” a person becomes more likable over time. Facial hair also grows on a person's face in the plain physical sense. The opening sounds like an ordinary change of opinion, while the last three words reveal that the speaker may simply be describing a beard. Deliver it casually and avoid emphasizing the pun too early. It is strongest when listeners briefly believe they are hearing a sincere confession before the literal meaning appears.