To the OP,
Well, kinda. I was absolutely shocked to get in at all, and then to get full-funding plus a fellowship, I thought for sure they must have confused me with another prospective student who happened to have my last name (which is uncommon).
But I've also visited the program, trying to rely on my intuition and skills of observation to see if there was any proverbial "man behind the curtain" to look for and. . . I didn't find one.
So now, it's just nightmares about my offer getting rescinded on ludicrous grounds, akin to the nightmares I had (both before and after my thesis defense) about flunking because I didn't know how to care correctly for dragons.
(What? I'm a creative person. . . )
Also, I agree with PsychChick - I know I was preparing myself for the worst, too, especially since I only decided to apply one place and knew all too well how easily this could have blown up in my face, so I was convinced I wouldn't be accepted. Made it an awfully nice surprise when I got the official notification!
Probably Imposter syndrome. . . I hear that's rather common in our particular demographic. . .