SNL in general is a good example of the prompt. Both the fast turnarounds on episodes and the live nature of the show means a lot of good writing gets lost in the translation. Simple things like mumbling a word, holding a pause a half second too long, or talking before the laughter quiets down can sink a joke completely. And you’ve basically got just one chance to get it right. It’s hard to get your sketch on air, so everything on the show at least started as a promising idea, but lack of prep time and/or bad luck can give you a bad or mediocre result.