Yup, that's the big news surrounding the Halo 4 appearance on Conan O'Brien tonight. Conan, along with sidekick Andy Richter, will have a small talking role of some sort towards the end of Halo 4.
Conan and team visited 343 Studios where they talked to Franchise Director Frank O'Connor and Executive Producer Kiki Wolfkill about Halo 4 and how Conan would be fit into the project. The segment ends with Conan and Andy doing some voicework, and rounds off with a quick look at Halo 4's multiplayer in action. Cool, I guess.
Halo 4 will be out on November 6 for the Xbox 360.