Big white 9x11 envelope, not particularly thick. It just has a folder with Nassau Hall embossed on the cover, and it contains your letter, financial aid letter, a map of Princeton, and a car decal. (At least that what it was for ED students. RD students might get more paperwork? Anyway, I'm excited. It means we get more mail!
Why would they send another application? Princeton doesn't accept transfers, so you either get in as a freshman or you wait until grad school. Those things can get expensive to print -- then they'd have to send them to thousands of people who will never use them?