Continuity mistake: In the scene where Barney is headed home from work right before his wife leaves him for the athlete, the sun looks like it's morning sun. After about 30-45 seconds into the conversation with his wife why she is leaving, the sun changes to a late afternoon. It is very apparent on the mailbox. The shadows completely change direction in a matter of minutes. (00:08:20)
Deliberate mistake: After the first scene where Hannah's ex-husband walks in without knocking and picks up the kids, Hannah is looking at some family pictures including her, her ex-husband, and the kids (supposedly taken when they were still married). But in the pictures they're all wearing the exact same clothes that they were in the previous scene. Could be a coincidence but that seems doubtful.
Revealing mistake: Vinnie places two coin-filled water bottles in the trunk of his car and closes the trunk. As he is walking around the car to get in, the back of the car suddenly sinks down, which by itself indicates a special effect, as springs don't behave that way. But in addition, the rear tires, which would appear flattened if under a heavy load, are completely unaffected by all that "weight."
Continuity mistake: When Vinnie takes Joan Cusack's kids to the ball game, pay attention to where they are sitting. When they first sit down you can see a row of people sitting in front of them. But after they sing the National Anthem (and all the shots after that), there is a railing in front of them.
Continuity mistake: When Vinny is telling the anecdote at the end about Christmas and he is interrupted by the hitmen, he moves the kids back and then dives behind some wooden pallets, and immediately pops up to shoot the guns out of the hitmen's hands. As Vinnie pops up to shoot, the stuntman's hand reappears in shot from the side of the pallets.
Continuity mistake: In the scene where Barney and Vinnie are on the plane to New York for Vinnie to testify, they are handcuffed, apparent as he reaches up to pay the flight attendant for his drinks. Seconds later in the same scene he asks for Barney's pen and their hands are no longer cuffed. When they subsequently get off the plane, they are again handcuffed.
Continuity mistake: At the end of the movie, Hannah is introducing Vinnie at the ballpark dedication. She is seen standing on an elevated podium with nothing behind her. In the next scene showing her on the podium not only do the support beams disappear but there are people standing behind her.
Continuity mistake: When Vinnie uses the price gun in the meat department he takes all the meat he used the gun on and puts it in his cart. In the very next scene he's seen trying to push the cart but he's having trouble because it's suppose to be filled with all those meats. The only problem is that there's no sign of the meat he just put in the cart and the cart is not even 3/4 full.
Revealing mistake: Near the end, when the little league ball field is under construction, mob hit men suddenly appear and Vinnie dives for cover behind a stack of pallets; as soon as Vinnie dives for cover, he almost instantly stands up behind the pallets and opens fire. Of course, Vinnie is played by two people in this shot: A stuntman (who dives) and Steve Martin (who stands up). Watch the right side of the screen, and you will see the shadow of Steve Martin crouched and hiding behind the pallets while the stuntman makes his dive for cover. As the stuntman dives out of sight, you then see Steve Martin's crouched shadow stand straight up.