Chester 'n Nester are two imaginary friends at Foster's who usually appear as background characters. Their only speaking roles were in the episode Beat with a Schtick. Chester is voiced by Tom Kenny and Nester is voiced by Grey DeLisle.
Chester is a beige animal-like friend with short brown hair wearing a light blue cowboy outfit, complete with a dark blue cowboy hat. He also wears a black belt featuring a hawk or an angel in the center and black cowboy boots. He also has hair on his chin and a strand of wheat in his mouth. Nester, however, is smaller than Chester and somewhat resembles Clyde, the orange Pac-Man ghost. His arms, hands, and feet are reminiscent of the Disney character Mickey Mouse. They both speak with heavy southern accents.
Chester and Nester both seem to have perky, laid-back personalities, similar to most cowboys. It also might be hinted that they were both created on the same day, making them non-identical, different appearanced twins. However, Chester is the one who does most of the talking, and Nester is the one who speaks less often. They somtimes finish each other's sentences, and while during Nester's part of the other sentence, he usually pops out to finish it off. Also, whenever anyone else says a sentence such as, "Bloo and the New Guy are gonna face off at four o'clock!" (as seen in Beat with a Schtick,) Nester will pop out to repeat it. It is unknown if they ever interacted with each other in the series, and what their relationship with each other is like. It may be a relationship having a bestest big buddy-little buddy feel to it, similar to other pairs exactly like that like Yakky Doodle and Chopper from Yakky Doodle. Also, Nester does not like anyone else hiding underneath Chester's hat, and will promptly kick them out (as seen when Bloo tried to hide under Chester's hat to avoid getting pummeled by the new guy.)
Chester and Nester are seen as two inseparable friends and are rarely ever seen apart. However, in The Big Cheese, there is a scene with Nester sitting on the ground outside of Chester's hat without Chester anywhere in sight. Nester is seen joining in a game alone with Eduardo, Mac, Bloo, Coco, Cheese, and two imaginary friends, hosted by Frankie to get Cheese to spill the code for the security system.