What is the longest show on Cartoon Network?

Answer 1

2 shows tie for the longest running on Cartoon Network | Ed, Edd n' Eddy (70 episodes, 01/1999 - 11/2009) & Space Ghost Coast to Coast (104 episodes, 04/1994 - 04/2004).

Answer 2

Spongebob Squarepants is still producing new episodes and debuted in May 1999.

It should be noted that The Fairly OddParents had their start on Oh Yeah Cartoons in 1998 but the series proper didn't begin until 2001. So they are in second.