This trailer features Valve's Erik Wolpaw speaking at N.Y.U. as part of the school's "Game Center Lecture Series." The topic at hand is Portal 2, the recently released puzzle/platformer sequel, and some of the thought behind how the game turned out. There is a write-up on this on Destructoid where some points of interest are transcribed, such as this bit on something that was cut from the final design:

Someone asked if Valve had cut anything particularly good from Portal 2, and after racking his brain, Wolpaw recalled that they had come up with a “Morgan Freeman, kind of, sphere,” but ended up not using it. No, seriously. “Like, you find him in this little ten-by-ten room, and he’s, like, the wisest guy about this ten-by-ten space. Doesn’t know anything about anything [else] -- is just blown away by the shit that’s five feet outside the ten-by-ten space -- but has a lot of advice that all, kind of, relates to things that were in the ten-by-ten space.” I wish I’d thought to ask if they had actually gotten Freeman to lend his voice to the sphere.