Doug: 33 years old
Rugrats: 33 years old
Ren & Stimpy: 33 years old
Animaniacs: 31 years old
Rocko's Modern Life: 31 years old
Ahhh, Real Monsters! : 30 years old
Freakazoid!: 29 years old
Dexter's Laboratory: 28 years old
Hey Arnold!: 28 years old
Cow and Chicken: 27 years old
Daria: 27 years old
Johnny Bravo: 27 years old
Angry Beavers: 27 years old
KaBLaM: 27 years old
Catdog: 25 years old
The Power Puff Girls: 26 years old
Courage the Cowardly Dog: 25 years old
Ed Edd n Eddy: 25 years old
Rocket Power: 25 years old
Fairly OddParents: 23 years old
Billy & Mandy: 23 years old
Invader Zim: 23 years old
Samurai Jack: 23 years old
Chalk Zone: 22 years old
Jimmy Neutron: 22 years old
Kids Next Door: 22 years old
Teen Titans: 21 years old
Danny Phantom: 21 years old
Foster's Home for Imaginary Friends: 20 years old
Avatar: The Last Airbender: 19 years old
Ben 10: 19 years old
Chowder: 17 years old
My Little Pony: 14 years old
Adventure Time: 14 years old
The Amazing World of Gumball: 13 years old
The Legend of Korra: 12 years old
Gravity Falls: 12 years old
Steven Universe: 11 years old

@Alexia:

Catdog: 25 years old
Angry Beavers: 26 years old
KaBLaM: 26 years old
Ahhh, Real Monsters! : 29 years old