My Sim only has one icon/moodlet at the moment, which shows he had a "fairly nice meal", and his happiness is green. But, he just rubbed his stomach, groaned, and had the Pepto Bismol icon above his h...
I don't know what this is. Medicine doesn't cure it though, (I tried) just makes the Sim "dazed" and still coloured like paint hit them. :D It seems random and happening to any Sim.