Doctor Who

Doctor Who is a British science fiction television series that depicts the adventures of a time-traveling alien known only as "The Doctor". Originally premiering in 1963, it is listed in the Guiness Book of World Records as the longest running science ficiton television series in history.

In the Big Bang Theory

 * Sheldon's Saturday morning ritual includes getting up at 6:15 am and watching "Doctor Who" on BBC America. This was once disrupted when Penny crashed out on the guys' couch.
 * A replica of a Dalek (one of the Doctor's most famous adversaries) is sometimes visible on one of the shelves in Leonard and Sheldon's living room.