WATCH THIS

  • "The Big Bang Theory" (8 p.m., CBS): Sheldon (Jim Parsons) makes a major scientific breakthrough, but he's not celebrating because he feels like a fraud.

  • "Project Runway: All Stars" (9 p.m., Lifetime): Alyssa Milano assumes the hosting duties for a new incarnation that starts off with a challenge to create a punk look inspired by rocker Debbie Harry.

  • "Scandal" (10 p.m., ABC): Guest-star alert -- Lisa Kudrow joins the show for a multi-episode arc, in which she plays a powerful politician who butts heads with Mellie (Bellamy Young). Meanwhile, the firm has a new client: A philandering senator who takes naughty photos of himself.

    Also Thursday:

    A photo from the production of Project Runway All Stars in New York on Friday, June 7, 2013.Photo: David M. Russell/AETN
    A photo from the production of Project Runway All Stars in New York on Friday, June 7, 2013. Photo: David M. Russell/AETN ( David M. Russell )

  • "The Vampire Diaries" (8 p.m., The CW)

  • "Grey's Anatomy" (9 p.m., ABC)

  • "White Collar" (9 p.m., USA)

  • "The Michael J. Fox Show" (9:30 p.m., NBC)

  • "Elementary" (10 p.m., CBS)

  • "Parenthood" (10 p.m., NBC)