Captain Green and the Eco-Teens was a non-violent cartoon that is seen in the episode "The "Good Old Days!"".
This cartoon is a parody of the 90's environmental cartoon, Captain Planet and the Planeteers, which involved a group of teenagers using elemental powers to battle polluting evil-doers and to summon a powerful superhero named Captain Planet. The characters of this show-within-a-show are a parody of Captain Planet, right down to the comically multi-ethnic band of teenagers.
When Timmy Turner's grandfather, Pappy, was babysitting him one day, he noticed that Pappy did not seem to like any of the things that younger people liked. After trying to show Pappy some of his cool things to no avail, Timmy gave up and went off to watch this cartoon. Pappy was also interested in cartoons, and watched alongside Timmy. Pappy was disgusted by the non-violent cartoon, and reminisced of the cartoons of his day which were more violent and not afraid to take risks. Timmy protested that the cartoons of his day weren't that bad, when Captain Green appeared on television and started doing a lame "Eco Rap", causing Timmy to acknowledge his grandfather being right, and he switched the channel to watch Poke Eye the Longshoreman.