What Chekhov Knew About Sitcoms

His heyday was long before the advent of prime time comedy but I often paraphrase Anton Chekhov whenever an aspiring screenwriter suddenly throws a contrivance into the third act that had nary a passing reference in the first or second. The objective is always the same: to try to jumpstart a floundering plot with a last-ditch surprise in order to keep it from dribbling off with a whimper.