Put it up there with the Simpsons and SpongeBob as a show that went on a decade longer than it should have. (2001-2017)

It actually did end after 5 seasons all the way back in 2006 believe it or not, and it was on a pretty high note too (At least compared with what was to come). But Nickelodeon made the fateful mistake of bringing it back in 2008 and letting it limp along for another 9 years.

After said revival, and as the years dragged on, the show added no less than 3 separate characters to the main cast in a desperate bid to keep the show fresh, which is almost never a good sign (One of whom added in the 2nd-to-last season, Sparky the fairy dog, was so hated that he didn't even come back the next season and his absence was never acknowledged, ouch lol).

It's sad cuz, like The Simpsons/SpongeBob, it actually could be a genuinely clever and funny show, but it was just stretched too far and for too long to maintain it's quality.

At least, unlike those shows, it actually was eventually allowed to die...after 16 years.

...And there's gonna be a live-action reboot series apparently...