Remember that thing from Batman? Joker creates cosmetics that cause the person to have a permanent rictus on their face? Better be careful. Your face will freeze like that.

Besides, you deserve to grin as much as you want! OH! OH! I just realized that with your grin, that big grin you get sometimes, that you resemble the original woodcut of the Cheshire Cat! Now, that's just cool! Cept for the pupils. That would be just scary. And the whiskers. but those would just tickle. Or... so I would think.