Continuity mistake: After the baby escapes from the crib, Greg walks past it looking for him and the gate to the crib is wide open. Next shot, the gate is closed and there was no time for him to close it.
Continuity mistake: All the glasses of wine and the bottle change position and amount of liquid during the dinner scene.
Continuity mistake: After the baby gets soaked with the toilet water, you see him being brought into a bedroom wearing a towel. Next shot the towel is underneath. The transition of him being undressed is missing, despite the audio being continuous and thus not revealing an ellipsis in the action.
Continuity mistake: When Greg is talking on the microphone towards the end, it appears in his hand. However, the next time he pops it off the stand, it makes a loud noise that wasn't there the first time.
Continuity mistake: In the first movie, Pam says she received a fax (MCAT scores) from Greg's parents in Detroit. We see in this movie that Greg's parents have lived in Florida for many years.
Continuity mistake: Toward the end of the movie, when Bernie is going to fight Jack, Jack's hands are on his hips then in the next shot they are down.
Continuity mistake: After Bernie accidentally kicks Greg's face and then the argument starts out front by the RV, the sun is shining when either Jack is shown and/or the Fockers and Pam from their backsides but every time the Fockers and Pam's faces are shown, there is no sun on them at all (through from that angle it should be shining on their faces).
Continuity mistake: The empty rum bottle that was placed on the table in the room during the families arguing disappears after the Fockers walk out of the room.
Continuity mistake: After Jack leaves the whole group Greg phones him and then puts the phone on the table. Its position changes between shots.
Continuity mistake: When Bernard lies in front of the RV there's a sunny spot a meter away from his head which becomes shadowy in the close-up. This swaps back and forth.
Continuity mistake: From a wide angle Greg is covering his bloody nose with the palm of his hand when Roz hugs him. A shot later, in the close-up, he covers it with the side of his hand. Then there's a different angle, and afterwards it cuts back to the first wide angle with the initial palm-of-the-hand position.
Continuity mistake: Before Bernard leg-kicks Greg, Jack's arms swap from crossed to down by his side between shots with no time to lower them.
Continuity mistake: When Bernard tells Jack that he's gonna kick his ass, Bernard's position changes between shots: sometimes he has his back to the road in front of the RV, others to a flower bed sideways to the RV.
Continuity mistake: When Greg is giving his speech-of-truth at the party he extends his right arm and points at Dina. From the opposite angle his arm is lowered.
Continuity mistake: At the party Bernard proposes a toast to his son and raises his left arm. From the opposite angle his arm is lowered.
Continuity mistake: After sticking the needle in Greg's neck Jack extends his left arm and puts some cotton on the wound. A shot later his arm is suddenly lowered.
Continuity mistake: The position of the sodium filled needle on Greg's neck changes between shots: Sometimes close to the ear, others way below.
Continuity mistake: At the party, before Dina strokes Jack's ears her left hand is either on his chest or not depending on the shot.
Continuity mistake: During Roz's massage, when she says "unleash the beast", in the close-up shot her hand disappears from Jack's shoulder.
Continuity mistake: During the massage scene, after Roz takes Jack's shirt off he raises his head. In the close-up it's pressed against the pillow, then angle cuts back to his head raised which he then lowers.
Answer: Truth serum doesn't automatically make you speak the absolute truth - all it can do is make you say what you believe to be the truth. If Gaylord believed himself to be Jorge's father, then he would say that under the truth serum, even if it ultimately turned out not to be the case.
Tailkinker ★
Gaylord (Greg) was also drunk when he went on his monologue of spilling "secrets" about others in the room.