2. Patrick Stewart
Star Trek: The Next Generation has been the most represented show on The Big Bang Theory as far as celebrities go. Wil Wheaton is a recurring character, and Brent Spiner and LeVar Burton have made brief appearances. Well, why not have the captain himself appear? While not the original captain of the Enterprise, Stewart as Jean-Luc Picard was still one of the best performances Star Trek has ever produced. I may get yelled at for this, but in some ways I prefer Picard to Kirk. Just my preference. Not only has Stewart played a great Starfleet captain, but he also brought the X-Men together as Professor X in the X-Men movies. Like Hamill, he represents two franchises that the characters love. With his Shakespearean demeanor and unforgettable voice, Stewart can bring both class and hilarity to his appearance. What would bring the most humor? Have Stewart hang out with the guys. Playing video games, talking comic books, whatever. I want to see Stewart show his inner fanboy to an audience of millions!