|"Brain's Chess Mess"|
|Number in season:||6b|
|Original Airdate:|| May 6, 2013|
May 6th, 2013
April 16, 2013 
December 17, 2012
|Written by:||Peter K. Hirsch|
|Storyboard by:||Allan Jeffery|
"The Last Tough Customer"
Brain starts a chess club at school to improve his game and beat Los Dedos, the local chess master. Who knew the best player in the club would be… Rattles?!?
The episode starts with Brain who lost to Los Dedos in a chess match. So he makes a sign-up list for a chess club. After a game with Brain, Mrs. MacGrady goes to prepare lunch. Brain tries to correct people's problems, but they didn't pay attention. Then during a lecture, Rattles shows up and wins against Brain. So Brain goes after him. He promises free ice cream and him doing homework. He finally agrees. So he recruits Brain, George, Fern, Binky, and Buster. They were great. The day of the chess match came, and Brain won.
- Los Dedos is Spanish for "the fingers" and she is called that because she drums her nails when she plays and Brain says that it drives her opponents crazy.
- Rattles is revealed to be a skilled chess player.
- When Mrs. MacGrady and George first sign the sign up list for chess club, they write in black/pencil color. Later, Mrs. MacGrady's is shown as red and George's is blue.