A built an entire 10 adventure side quest directly as a result of the assumptions players made to my rolling for if they noticed the bread was day old and they all failed. Since no one noticed anything out of place, (various immediately "for no reason" needed to look for something in their packs later), as the paranoia grew I just rolled with their assumptions until the story was mostly fleshed out. To this day none are the wiser and think it was pure genius how I came up with all that outlandish stuff ahead of time.