Occasionally, I have a facial tick. It doesn't happen often, but it's kind of distressing when it does! I could be in the midst of a benign conversation, smiling, and all of a sudden a corner of my mouth will kind of turn downward into a frown. When this happens, I normally feel like bursting into tears. I'm not sure if it's a nervous thing or not. Normally, I'll bite the inside of my lip to keep it from quivering. I've always thought this was a strange quirk of mine and have never heard of anyone having something like this.