When Focker is getting his polygraph test, you can see the paper moving and the needles sliding in the closeup, but when it gets to a shot of both Focker and Jack, you can see the paper isn't moving.
If I remember correctly, in the beginning of the movie when Gregg is telling her parents about his last name, they spell it Fauker? I'm pretty sure that's right, not Foker.
Good eye. The moving polygraph probably was too much of a distraction for what they were trying to show and didn't think anybody would notice it was off.