Intended to air as the finale of The Angry Beavers on November 2001, Nickelodeon produced a standard double-feature episode titled "A Tail of Two Rangers/Bye Bye Beavers". While not much is known about the first segment (besides that fact that Norbert and Daggett try to become park rangers), it was the second segment that caused controversy amongst Nickelodeon staff and led to the entire episode never being aired.
The plot of "Bye Bye Beavers" involves the beavers receiving mail alerting them to the fact that their show has been canceled, with Norbert then having to break the news to Daggett that they are both, in fact, cartoon characters. They go on to break the fourth wall, with the voice actors calling each other by their real names (and by the names of other characters they voiced in different TV shows) and criticising the fact that after cancellation, cartoons continue to rerun without any payment being received by the creators. At the end of the episode, they both begin vanishing before yelling "APRIL FOOLS!" implying that the episode was not intended to be the last (this went on to spawn a rumor that the show was canceled because of the "Bye Bye Beavers" segment), though most believe this to be false, and believe that the creators made the segment in retaliation to the show being canceled.
Nickelodeon was far from pleased with the episode, namely due to the criticism of reruns, and the fact that it broke a Nickelodeon "rule" which stated that no final episode of a show is allowed to allude to the fact that the show is ending. As such, neither segment from the episode was ever broadcast (although there are claims that it was broadcast in Australia and Europe; these claims, however, are entirely unverified).
In 2006, during a podcast interview with Richard Horvitz (who voiced Daggett) on avimelman.com, the audio for the "Bye Bye Beavers" segment was played, and has been rapidly circulated since. Is it not currently known (though speculation is rife) as to whether the episode ever reached the animation process (as no visual evidence of it has ever turned up). Some doubt the legitimacy/completion of the leaked audio, due to the laughter heard in the background (assumed to have come from crew members); in fact, this laughter actually came from host Avi Melman and Horvitz, while podcasting the clip. While rumors surrounding this episode abound (all mostly unverified), it is doubtful we will ever see the finished product, as even if the episode was animated, due to the nature of its removal from broadcast, it's unlikely that Nickelodeon would ever see a reason to release it.
UPDATE 5/2/15: Yesterday, Uncle Sporkums discovered an alternate link to the "Bye Bye Beavers" audio. Cheers!
UPDATE 10/14/16: There seems to be a mixup with the production codes, on 26 October 2016 at 12:30 am the episode titled "Things That Go Hook In The Night"/"Specs Appeal" will be "premiered" as it is the first time it is shown on The Splat. It has been released before Season 4 Episode 9 on 6 January 2001.
Nickelodeon storyboard artist Maureen Mascarina has leaked twelve pages of her work on the storyboard onto her official website.
- The full 2006 avimelman.com podcast featuring Richard Horvitz. Retrieved 14 Feb '13.