A "Guest Star" refers to a well-known actor or celebrity who appears in a single episode or a limited number of episodes of a television show. These appearances are often meant to attract viewers and add excitement to the storyline. Guest stars can play a variety of roles, from friends and family members to antagonists or special characters that enhance the plot. In many cases, guest stars are recognized figures from other shows or movies, which can create buzz and draw in audiences. Popular examples of guest stars include Matthew Perry on The Good Wife and Lady Gaga on American Horror Story. Their involvement can lead to increased ratings and renewed interest in the series.