As a part of the physical aspects of kerbals there should be a random encounter ,or it could be joined with the stupidity factor, that during launch or upon achieving orbit the kerbal on board vomits. The animation adds a comedic value that the emotion faces already show. It could be something like a greenish splat on the visor of their helmet and gets cleared after a short while. This animation could also be used with space planes when they go spinning wildly. I'd never thought about this idea until my girlfriend asked me if they did vomit while she laughed at the faces they were making during the launch.