Do not purchase the ordinary DVD, because it only has the film in 4:3 format.
I'm boggling at this decision. I am surprised that there would be people advanced enough to have DVD players but Luddite enough to have 4:3 televisions (having been using widescreen for all of a year, 4:3 actually looks wrong now), but Richard has pointed out that televisions cost a lot more than DVD players. I think the thing that amazes me about this is not so much that some people would still be watching in 4:3 so much as the decision to release it only in 4:3! "A Bug's Life", which came out 2 years ago, had 16:9 on one side of the disc and 4:3 on the other.
At the cinema, films are shown at an aspect ratio of 1.85:1. Widescreen TVs are 16:9, or 1.77:1 - old TVs are only 1.33:1. For years, film purists have insisted that you should watch films at home in the same aspect ratio that you do in the cinema - why should you lose some of the picture? This argument applies doubly to something like "Monsters Inc" which is done entirely in CGI. I've been to a Pixar masterclass, where they showed us just how much time and effort goes into rendering all the little details - I don't want to miss any of the picture. So why release something in sodding 4:3?
I suppose Disney might have been thinking that people would give the film to their kids to watch on the household's second TV, which might well be older than the primary one - but in that case, they should have said that it was in 4:3 in really big letters on the box. No, this is just a marketing ploy to get people to buy the "Collectors' Edition". But it sucks! We were extremely lucky that the shop we bought it from let us take it back, even though it had been unwrapped.
The really daft thing is that the menus and some of the trailers on the "Monsters Inc" DVD are all in 16:9 - even on the version of the disc which has the film in 4:3! So anyone actually viewing it on a 4:3 television will get a letterboxed picture for these features. Yeah, that makes sense - grrrr.