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What’s on TV Thursday: ‘Klepper’ on Comedy Central

The Big Bang Theory The smart, popular comedy ends its 12-season run with a one-hour finale. Johnny Galecki, Jim Parsons, Kaley Cuoco, Simon Helberg, Kunal Nayyar, Melissa Rauch and Mayim Bialik star. A half-hour retrospective special airs later this evening (see below). 8 p.m. CBS