When Lucy and George are arguing at the children's benefit, it is alternately raining/not raining between shots. Similarly, George's tux jacket is wet/dry.
When George and Lucy abandon her car to get her to the toilet of the RV, George leaves the windshield wipers going. Later when the RV passes the abandoned car, the windshield wipers have stopped.
During the Charity Ball, June is wearing a sheer, almost see through dress. As June and Wade enter the elevator, during the elevator scene and as they enter the apartment, you can see June's areolas through the top. Then, when Lucy comes into the apartment and catches June in a state of near undress, she is now wearing a opaque solid black strapless bra. She could not have been wearing that particular bra in the previous scenes.
When Norman is leading June into Lucy's office, we can see Lucy's reflection look up and watch them come in. However, when the shot moves to Lucy, she is still wiping off the front of her shirt, and has no clue they have come in until Norman gets her attention.
While George and his driver are playing chess, George makes a move, they talk a bit, and George makes another move. The driver never touches a piece.
The title, if grammatically correct, would read Two Weeks' Notice, not Two Weeks Notice.
As George and Lucy are walking towards the RV while stuck in traffic on the overpass you can see a white lane line dividing the two directions of travel. A white lane line between two lanes indicates both lanes are in the same direction of travel - a yellow line would indicate opposite directions as attempted here.
When Lucy and George are flying around Manhattan in the helicopter, they are clearly not actually flying because the lighting on their faces does not change as the helicopter rotates and flies between the skyscrapers.
During the "stapler fight" the actresses lips have no relation to the audio track.
When Lucy comes out of the hotel after catching George and June playing chess, a crew member is reflected in the window.
When George meets Lucy's parents for the first time and they invite him over for cake because they only live two blocks away, you can tell it's over a mile. When they start leaving the construction site, there is a large tower they start walking towards with a large construction crane about 1/2 a mile past it on the right. However, immediately when they get to the apartment roof, you can see the crane below about 1/2 a mile up the beach, and the tower is over a mile away now.
When Lucy is talking with her father in the kitchen, you can see the reflection in the television of a boom mic and wires taped on the ceiling.
At the tennis match, when George says the score he says 30-0 and then serves to the wrong side of the court