I also like how in Episode two, they explained the relationship between Aperture Science (Portal) and Black Mesa, how they were rival companies competing to create the first teleportation technology, and Black Mesa won, how ever much of a failure it was.
Also: For the end credits, they recorded this song sang by GLadOS (the evil computer in Portal). Warning: Semi Spoileresque, but its such a good song...
Its called "Still Alive", and you would understand the lyrics a lot more if you beat the game (it only takes 3 hours).
http://www.gametrailers.com/player/u...ylist=featured