During the part where De Niro is handing out the rehearsal schedules, he says something like, "Here are the revised schedules." In a deleted scene included on the DVD, the family is going over the schedule earlier in the movie, and there are a few errors on it. That's why De Niro said "revised schedules".
If Deniro made an intentional reference to something that happened in one of the deleted scenes, how is that a slip-up? Also, who's to say the scene didn't actually "happen" in the world of the movie, even though we didn't see it on screen?
The scheduals are revised because Greg is the new Usher (or whatever he is) because the other guy is sick. It's the Invitations that are messed up in the deleted scene.
I've not seen the deleted scenes but through the natural course of the movie i had assumed that the schedule had been revised to remove DR Bob's friend as the usher and replace him with Focker?
Albert, I agree that this is not a slip-up. Just something I noticed. But Beau433, it's not the invitations in the deleted scene; it's the rehearsal. Remember "Surf & Turd" restaurant where they will be having the rehearsal dinner?