Easter egg: Inside the 2nd disc, go into Humans Only. Select the Production Tour, and watch the 6 clips, or you could hit >>| until the chapter reads 7. You should enter a menu with doors like the ones from the intro, only red and orange (something like that?). Check behind each of the front 7 doors.
Easter egg: In the 2nd disc, choose the Monsters Only door. Hit right to highlight the eye on the logo on the place where Celia takes the calls. Hit enter and you'll find clips that the crew made, using scenes from the movie, but not actually following it.
Easter egg: 2nd disc: Go into Humans Only, and choose the Pixar door. Highlight the Monster's Inc logo by hitting down, and then hit left to circle the paper plane, or highlight the path of the plane. Hit enter, and you'll see footage from a paper plane show they had.