The Big Bang Theory/The Toast Derivation
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The Toast Derivation is the seventeenth episode of the fourth season of The Big Bang Theory, and the eightieth episode overall.
Starring: Johnny Galecki (Dr. Leonard Hofstadter), Jim Parsons (Dr. Sheldon Cooper), Kaley Cuoco (Penny), Simon Helberg (Howard Wolowitz), Kunal Nayyar (Dr. Rajesh "Raj" Koothrappali), Mayim Bialik (Amy Farrah Fowler), Melissa Rauch (Bernadette Rostenkowski)
Special Guest Star: LeVar Burton (Himself)