A sitcom, clipping for situational comedy (situation comedy in the U.S.), is a genre of comedy centered on a fixed set of characters who carry over from episode to episode. Sitcoms can be contrasted with sketch comedy, where a troupe may use new characters in each sketch, and stand-up comedy, where a comedian tells jokes and stories to an audience. Sitcoms originated in radio, but today are found mostly on television as one of its dominant narrative forms. This form can also include mockumentaries. A situational comedy television programme may be recorded in front of a studio audience, depending on the programme’s production format. The effect of a live studio audience can be imitated or enhanced by the use of a laugh track. During filming productions, the laugh track is usually pre-recorded. Critics disagree over the utility of the term "sitcom" in classifying shows that have come into existence since the turn of the century. Many contemporary American sitcoms use the single-camera setup and do not feature a laugh track, thus often resembling the dramedy shows of the 1980s and 1990s rather than the traditional sitcom. Other topics of debate have included whether or not cartoons, such as The Simpsons or Family Guy, can be classified as sitcoms.