Every performer eventually has had that one truly terrible moment on stage.
While promoting his new book, Silver Screen Fiend, on Late Night with Seth Meyers, Patton Oswalt also entertained the audienced with the story of the worst time he ever failed on stage as a comedian. Without giving away all the gory details, it involves a lot of DayQuil, hecklers and some projectile snot (and other bodily fluids).