On The Big Bang Theory (7 p.m., CBS/Ch. 2), Sheldon (Jim Parsons) would seem to be entirely predictable. Incredibly annoying, but predictable.But it turns out he has a secret. And Howard (Simon Helberg) and Raj (Kunal Nayyar) are determined to uncover the secret why Sheldon disappears every afternoon at 2:45.Now I want to know, too.Elsewhere on TV ...NFL (6 p.m., NFL Network): Miami Dolphins at Buffalo BillsLast Resort (7 p.m., ABC/Ch. 4): Somebody stole the nuclear launch key.30 Rock (7 p.m., NBC/Ch. 5): Tracy turns Jack into a villain in a movie.The X Factor (7 p.m., Fox/Ch. 13): Contestants face elimination.The Vampire Diaries (7 p.m., CW/Ch. 30): Elena suffers terrifying hallucinations.Project Runway All-Stars (7, 9, 10 and 11 p.m., Lifetime): The contestants have to draw inspiration from images sent to them by USA Today readers. Which sounds sort of stupid.Two and a Half Men (7:30 p.m., CBS/Ch. 2): Walden becomes an older woman's boy toy.Up All Night (7:30 p.m., NBC/Ch. 5): Scott plans a Thanksgiving dinner for divorced dads.Person of Interest (8 p.m., CBS/Ch. 2): The latest POI is a brilliant surgeon.Grey's Anatomy (8 p.m., ABC/Ch. 4): Bailey tricks Arizona into assisting on a case.The Office (8 p.m., NBC/Ch. 5): The women in the office try to teach Dwight how to interact with women.Glee (8 p.m., Fox/Ch. 13): Rachel and Kurt visit Lima.Beauty and the Beast (8 p.m., CW/Ch. 30): Catherine thinks Vincent stood her up.Parks and Recreation (8:30 p.m., NBC/Ch. 5): April and Leslie fight over a proposal for a dog park.Elementary (9 p.m., CBS/Ch. 2): Sherlock investigates a double murder that may be tied to a crime that took place 13 years earlier.Scandal (9 p.m., ABC/Ch. 4): Fitz and Cyrus face the ramifications of James' front-page news story.It's Always Sunny in Philadelphia (11 p.m., FX): Mac, Charlie and Dee struggle with their faith.Jersey Shore (11 p.m., MTV): Jenni plans a shower for Snooki.