When Jack Byrnes is calling his contacts for information on Andi he starts to use the phonetic alphabet to spell her name. A-D are correct... Alpha, November, Delta. However, he says Indigo for I. The correct word for I is India.
When Jack Byrnes searches on Google, location contains search condition "jack burns" while Google search field contains "jack byrnes." Also the screen is from Internet Explorer while search has the Safari browser as the client.
When Greg cuts his finger carving the turkey, the blood spatters onto Jack, hitting him in several places including his face, across his chest, and on his left arm and shoulder. When the camera cuts, the blood that was on his arm and shoulder is gone.
When Greg is talking to Jack on the phone about being the Godfocker, Greg's finger nails are long, in the next scene, right after the phone call and before Greg's son throws up on him, his finger nails are cut short.
When Greg starts backing up the truck, it's clearly centered on the paved driveway. When everyone is running to rescue Jack after the sand spillage, the truck has been repositioned several feet to the left of where it was and the wheels are now on the grass.
While talking privately with Greg, Jack implies that his son, Henry, is just like his father, Greg. Jack reasons that he has been doing research on twins and found that sometimes, one child will get an extra chromosome from the father's DNA in the sperm. While that might apply to identical twins, it could not be possible for Greg twins. Greg's twins are male and female and developed from two different eggs that were fertilized by two separate sperm.
The goof items below may give away important plot points.
When Jinxy has Arthur the lizard in his mouth and Greg gives him the Heimlich Maneuver to make him spit it out, Jinxy can be heard letting out a loud hiss. Cats cannot hiss with their mouths closed. If he really was hissing, then the lizard would have fallen out of his mouth and there would be no need for Greg to perform the Heimlich Maneuver.
Bernie is able to get a genealogical DNA test done on Jack by snipping his pubic hairs. Pubic hair does not contain DNA but the root does. So in order to get the test done, he couldn't have snipped the hairs, he would have had to pluck them.