The iconic guest stars of The Big Bang Theory have provided this comedy series with many of its funniest moments. Featured in these eight landmark episodes, handpicked by the show’s creators and producers, are such scientific luminaries as Stephen Hawking and astronaut Buzz Aldrin; Sci-fi superstars including Star Trek’s Leonard Nimoy, George Takei, Wil Wheaton and Brent Spiner, The Sarah Connor Chronicles’ Summer Glau, Battlestar Galactica’s Katee Sackoff; Comics marvel Stan Lee and the legendary Bob Newhart.