When Joy goes to work the day after moving in with Jack she is wearing a blue dress. When her boss tells her one of the ladies will be promoted she is wearing the gray dress she had on in the opening scene. when she returns home she is in the blue dress again.
The scene where Joy is bombarded with files on her desk before the scene where Jack is punched, appears again when she is talking to her boss about the birthday party she went to, with her wearing the same outfit.
When they are playing the slot machine talking, it actually would have paid a small amount with the jackpot symbol-jackpot symbol-seven before they actually put the borrowed quarter in and hit the jackpot.
After Jack's father makes the last shot to win their basketball match, the ball can be seen swishing through the hoop and bounce a couple of times, on the next wide angle shot showing his father walking away, the basketball is no where to be seen.
During the "flashing" montage of Joy and Jack getting together in their hotel room after their drunken night in Vegas, there is one shot where they are lying in bed and a crew member is visible in front of them.
When Joy shows the marriage counselor a video of Jack and his two friends fighting outside her apartment with her cell phone, you can clearly hear their voices, but in reality there was no way to record their voices from her window.
The initial shot of the Las Vegas "strip" shown just after both sets of characters leave New York was printed optically reversed; the casinos are on the wrong sides of Las Vegas Boulevard S and the signs for Bellagio and MGM Grand and the on-building sign for Monte Carlo can all clearly be seen to be mirror-images.
At the end of the movie, Jack is seen crossing the Robert Moses Causeway and Captree Bridges from Long Island to Fire Island, but in the next scene it shows him crossing the ferry from the mainland to Fire Island.
Joy is so wasted, she doesn't realized what happened until the morning after, yet later berates Jack for buying her wedding ring out of a vending machine. However, the if the ring was plastic or fake is was probably very obvious that it was bought from a vending machine, or she used the term in mockery, which isn't uncommon.
Hater tells Jack that a Las Vegas marriage can only be annulled or dissolved in the state in which the parties reside. As evidenced by the fact that Louisiana resident Britney Spears's first marriage was annulled in Las Vegas, where it took place, Hater is wrong. However, he is a pretty lame lawyer so this is not necessarily a goof.