Last night on Conan, Zachary Quinto, two-time serial killer in a TV series (Heroes and now American Horror Story), gave away the secret to his way-too-convincing murderous look: his dark bushy brows angled just so. Plus: Stephen Colbert expressed his beef with Gandalf a.k.a. Sir Ian McKellan. “My fear is that you don’t just make gay seem acceptable, which I got my own problems with,†Colbert pointed out, “You make it seem heroic.†Well, fear some more, because there will be a sequel, promised McKellen, in which “Gandalf the Gay†cavorts with “his favorite dwarf.†Also, an all-star version of “Guess That Tune†had Keira Knightley, Dave Matthews, Michael Bublé, and Jimmy Fallon scrambling to play children’s songs on bizarre instruments including a teeny-tiny harmonica; and Jon Stewart ragged on the Christmas coaster “book†that Denis Leary had “written.†Watch the compilation to see what you missed.