Continuity mistake: Two totally different locations are used for the exterior of Darcy's new apartment. When Nick stands outside trying to get Darcy to answer, the building has no steps leading up to it and has a rectangular art deco style front door, flanked by two window panels. In the closing scene, which takes place the same day/evening, Nick is supposedly visiting the same building as earlier, but this time it has steps leading up to an arched front door and has a completely different facade. This can't be explained by one apartment being her old place, the other her new place, as not nearly enough time has elapsed in this sequence to make such an explanation possible.
Revealing mistake: When Nick drops the blowdryer, and it's moving in slow motion toward the tub, why is the blowdryer casting shadows on the ceiling directly above the tub? That would mean there are lights either in the tub or on the floor right next to it. (00:29:00)
Continuity mistake: When the old Chinese granny shows Mel where to go, she is shown holding the umbrella with him, one shot, her hand is above his, and in the next shot it is below his. (01:42:50)
Factual error: When Nick is in the psychiatrist's office and tells her he can read women's minds, Bette Midler's character says, "Sigmund Freud spent his entire life trying to understand what women want," or something to that effect. Actually, Freud didn't care much about the psychology of women, he simply passed them off as having "penis envy". Most psychologists today recognize that Freud was a little off base. It seems like the writers just used Freud's name because he's the only psychologist the general public would know by name. (00:49:10)
Continuity mistake: When Nick meets Alex's boyfriend for the first time, Cameron's necklace changes from one style to another then back to the original between shots.
Continuity mistake: During the entire scene when Darcy is first introduce and handing out boxes, the position of her hair keeps changing. At times one side is along her back then it is on her front side. Also both sides are doing the same, being either in front or back.
Continuity mistake: After Nick has tried on the pantyhose, there 2 small towels on top of 2 bigger ones on the towel rack. They appear to be neatly folded and even. The scene cuts to his daughter walking in then back to Nick. The small towel on the left side is now shorter in length and not neatly placed.
Continuity mistake: When Mel is kissing the girl from the coffee shop outside her house, she tilts her head to the her left. In the next shot, she is to the right. (01:00:50)