A series finale is the last episode of a television series. It wraps up the series in a way which provides a clear resolution, sometimes leaving the door open for the continuation of the series in the form of another medium such as a film or comic book. Series finales tend to be rather extravagant productions, since they are the last hurrah of a television series.
In the series finale, the huge plots which have loomed over multiple seasons are finally resolved, and some sort of resolution is provided for the characters. Some may go on to live happily ever after, while others may be killed off. Sometimes, small mysteries are left unsolved, to give the show an air of tantalizing mystery, or to avoid infuriating fans who may be expecting a particular outcome. It is common for actors who appeared in earlier seasons to make a guest appearance in the series finale, as a way to say goodbye to their characters and the series itself.
Some television shows have been specifically designed with a set end date. In this case, elaborate planning may go into the series finale, and the producers and writers may work together to lay the groundwork over the course of several seasons. In these cases, it is not uncommon for the series finale to last two or three hours, to accommodate all of the necessary scenes and dialog.
In other instances, it may become clear that a show is going to stop airing at the end of the current season, in which case the producers decide how they want the show to end, and use the episodes at the end of the season to ease viewers into the series finale. Sometimes this is a natural evolution, with producers and networks agreeing that a show has run its course, and in other case it is the result of controversy, poor ratings, or other problems with the show.
On occasion, a season finale has stood in as a series finale. This occurs when a show is canceled or not renewed after the last season has already been shot, a not-uncommon occurrence, since filming usually wraps a month or more before the season finale airs. When a network decides not to renew a series, it may opt not to air the remaining episodes at all, or to move the show to an unpopular day in the schedule. In some cases, the network may allow the producers to edit or partially reshoot the planned season finale to provide more resolution for the fans.