The Big Bang Theory Sheldon (Jim Parsons) secretly goes to work for the military, without telling Leonard and Wolowitz (Johnny Galecki, Simon Helberg). Dean Norris (“Under the Dome”) reprises his guest role. Melissa Rauch, Kunal Nayyar, Kaley Cuoco and Mayim Bialik also star. 8 p.m. CBS
Supernatural Sam, Dean, Jack and Castiel (Jared Padalecki, Jensen Ackles, Alexander Calvert, Misha Collins) head west to solve a murder, and Dean gets involved in an old-fashioned gunfight with a famous gunslinger in this new episode. 8 p.m. KTLA
Grey’s Anatomy The hospital falls victim to a computer hacker, affecting every...