Final episodes of TV series tend to get very high ratings, particularly if the show is already popular. The finales of "M*A*S*H," "Cheers," and "Seinfeld" are some of the highest rated episodes of their respective programs, as well as some of the highest rated episodes in television history.
The series finale of "M*A*S*H" was the most watched television event in American history, until it was surpassed by the 45th Super Bowl in January 2010. The finales of some long running shows received a ratings boost due to media buzz surrounding these finales. "Lost" and "Breaking Bad," two shows with a focus on mysteries and plot twist, received large ratings boosts for their finales due to public curiosity as to how they would end.