Tics involving smiling and frowning come from an urge to do so, not from happiness or sadness. Like all tics, these can be stressful to experience and impact mental health.
This tic- similar to laughing and crying tics- may occur at times we least want them too.
Any tic can work this way. However tics displaying a ‘fake’ emotion may pop up in an environment that contradicts the emotion. This could be a child smiling when being told off by a parent. It could be a frown when getting a promotion at work.
Tics can work in mysterious, cruel ways. Giving people an impression of us that is not at all the reality.