The enitre cast of the The Big Bang Theory–Johnny Galecki, Jim Parsons, Kaley Cuoco, Simon Helberg, Kunal Nayyar, Mayim Bialik and Melissa Rauch–is visiting Conan Wednesday night in anticipation of the show's 200th episode, airing Thursday night on CBS.  

What better way to celebrate than to throw Sheldon a birthday party?  Because we all know how much Sheldon loves a birthday.