Lester is the cousin of Ace and Chet, and is a bad apple. He is first introduced in the Game Genie episode. Lester gets Ace and Chet hooked on cheat codes, and makes them trade some of their games for his game genie and code book. Lester was later busted and sent to rehab after Dad found out.
Lester came back for Christmas after getting out of rehab. This time he showed Ace and Chet his new Sega Genesis, and convinces Ace to sell out his brother and ask Santa for a Genesis instead of a Super Nintendo like they agreed. Again, Lester got caught, and hasn't been seen on the show since.
Despite the similar appearance, Lester is not the Angry Video Game Nerd.