Last Night Summary: So 50 Cent cancelled his appearance on Conan a couple hours before the show because he felt he was coming down with a cold? Stern and Gaffigan were good as usual on Conan. Also: "The Office" was fantastic; I was amazed at how long Colbert allowed his druggie guest to ramble; kid scientists on Letterman were typically cute and funny and I'm hoping for a new set of stupid human tricks......