65th Episode Rule

The 65th Episode Rule was a controversial rule that applied to all Disney television shows, stating that no show can go beyond 65 episodes (2 or 3 seasons). This rule angered many Disney Channel fans, due to the fact that many shows had been canceled while they still had a large fanbase (such as Lizzie McGuire and Even Stevens). Due to the popularity of That's So Raven, Disney ordered more episodes. Disney later discontinued this rule, allowing shows like Kim Possible to be renewed for a fourth season on November 29, 2005.

Exceptions to the Rule When it Was Active
As of October 2013, Phineas and Ferb is the longest-running show, with 117 episodes and counting and a movie.

Kim Possible was originally ended after 65 episodes. Due to popularity the show was eventually picked up for a 4th and final season. The show is considered the turning point for the rule being phased out.

Rationale
The cut-off point of 65 episodes may have more to do with programming schedules than any personal feelings about a series on the part of studio executives. With 65 episodes, one episode can be broadcast each weekday, reaching the 65th episode at the end of the 13th week (5 x 13 = 65). Thirteen weeks is one quarter of a year. Four 65-episode shows can be broadcast in a calendar year.

At the time the 65th Episode Rule came to the public's attention, networks were beginning to move away from rigidly-defined schedules, where a weekly show would run for 13 or 26 weeks straight, followed by the same number of repeats. This change has further been accelerated by the following factors:
 * Dedicated channels such as Disney Channel, Cartoon Network and Nickelodeon, rather than relying on syndication to fill afternoon and weekend morning programming times
 * More ratings-driven decisions and fewer instances of allowing shows to find an audience even if the ratings are not as high as desired
 * Shows being canceled before a current season is completed, requiring new shows being developed more frequently to replace them
 * New technology like DVRs and episodes being made available on network websites, which allow viewers to watch shows on a schedule of their choosing

Currently, the number of episodes in a season varies from show to show, with 22 to 26 being a common amount for a "full" season. In addition, a season can be split into two segments, with the second segment being referred to as a half season (season 1.5, season 3.5, etc.) or even as a "new" season. All of these factors make it difficult for a modern show to reach the 65-episode mark any longer and can just as easily end with fewer episodes as having more than 65 episodes.