When Eddie and Miranda are crawling back onto shore (after Eddie jumps into the water to save Miranda), you see an overhead shot in which the back of Eddie's shirt is intact. Seconds later, the back of his shirt has a huge rip up the middle, revealing a jellyfish stuck to his back.
When Miranda falls into the ocean and Eddie jumps in after her, you can clearly see that Miranda is wearing aqua shoes in the water instead of her sandals; which she is wearing when she is walking out of the water on the beach.
During the wedding reception when Eddie meets Lila's mom, an Asian lady wearing a blue dress is dancing in the background behind Eddie. In the next shot, the same lady is seen dancing behind Lila's mom.
Opening Sequence of the film, Eddie and Doc are walking down a steep hill sidewalk and doc asks about "anything exciting" in Eddie's life. There are NO cars anywhere near them. The very next cut Eddie is answering the question and they are on a level sidewalk and there are cars parked in the street and behind them over doc's head. They also pass the same group of seated sidewalk coffee drinkers twice.
When Eddie's father walks in Miranda's room after Eddie gets caught at her bedside, his white cap is about to fall off while he says his line. In the next frame, his cap is suddenly perfectly straight again.
When Eddie is checking into the hotel you can see a boat passing in the ocean behind Tito, but when the camera cuts to Eddie then back to Tito the boat is gone, even though their wouldn't have been enough time for the boat to pass out of the scene.
In the diner when Lila asks Eddie to hold her hand while they eat, he puts his napkin in his lap and switches hands. When the camera changes angles his hand hasn't been changed. It goes back and forth a few times.
Eddie and Miranda are having drinks with the family after their day at the beach. In the first shot Eddie has a nearly emptied green colored drink. In the ensuing shots the color changes to white and the level of the drink changes periodically.
In the scene when Eddie talks to Miranda's family at their home in Oxford, Boo's hand is on Martin's right shoulder when shot from the front, but his hand is on Martin's left shoulder when shot from behind.
While Eddie and Lila are driving down to Mexico on the Highway, their car is filmed from the side, passing by. You can clearly see the reflection of the crane the camera was mounted on in their cars' side.
Miranda states she is drinking a Mind Eraser, however her drink is red and it has tequila in it - both not true. A Mind Eraser would not be either since it contains only vodka, coffee liqueur and soda water.
Ben Stiller gets stung by a jellyfish, and Malin Akerman has to pee on him to make the pain stop. This could make it worse. Mayo Clinic suggests rinsing with SALT WATER, removing stingers, and then use hot water for the area.
On the way to Mexico when Lila tells Eddie she wants him to find a hotel so they can have sex, the next shot shows their car taking the exit off the highway. There is however only one person still in the car and you can clearly see it is neither of the main characters but a stunt double.
The goof items below may give away important plot points.
Lila told Eddie that her cocaine abuse gave her a deviated septum (a crooked nose). Cocaine abuse can produce a perforated septum (a hole between the nostrils), which is what Lila has. Hilarity ensues as different items come through.
When Eddie is trying to tell Lila he wants to get a divorce, there are two glasses of water on the table, without any ice inside them. Later, after the cousin's intervention, the same glasses can be seen, but this time filled with trimmed ice.
At the end of the movie, Eddie moves to Mexico because he says that Lila got the store in the divorce. California is a community property state, meaning that all marital assets are divided in half at the time of a divorce. Therefore, Lila would not have been entitled to the store because Eddie already owned it before they got married, making it exempt from the marital assets. At the most, she would have been entitled to half of any income he made during their marriage, but they were married such a short time that it probably would have not been very much.