When Holly is in the kitchen pouring a glass of alcohol and is distracted by William, she pours most of it on the counter and only a small portion into the glass. However, when William enters the kitchen, the glass is full for a short period of time and then when they glance back at Holly it is almost empty again.
In the final scene hay appears and disappears on Williams' jacket.
Throughout the movie Holly's wedding rings change, they are sometimes a silver diamond set or a simple gold band.
When Holly is drinking with William in the kitchen in Ireland, her drink amount changes from when the camera is facing her to when it is facing William.
When Holly and her friends are in the boat and they all have their life vests inflated, when Holly's first opens, the blow pin cap is off. In the next scene that zooms in on her face, the cap is on.
When Holly and Daniel get into Yankee Stadium after hours, the batter's and baselines are perfectly drawn on the infield. These would not be present after hours. They are drawn with chalk and only put down after batting practice and just before the game. By game's end, they are worn away.
When the girls are rescued at the lake (fishing) as he pulls up it is clearly visible that the boat is anchored.
When Holly gets her first letter it reads, "I know you're still confused about that job..." But his voice says, "I know you hate your job..."
In the scene where Daniel and Holly are at the restaurant together, all of the wide shots of Daniel have the camera reflected in his wine glass.
In the boat scene, when the girls are being rescued and the image is a long-shot, you can see a cable keeping the boat steady. This is not an anchor, because they spoke about drifting to the shore.
When William is in the Kitchen with Holly and they do a close up on him when they are kissing, you can see a small mic on his shirt. In the next scene showing his shirt, it's gone.
After Denise and the club owner kiss for the first time she asks "What's my name?" and he responds "Tom.".
When Holly asks to design shoes for Denise, Denise references Pinocchio (1940) and asks, "What? Did you turn into Geppetto?" In Pinocchio (1940), Geppetto made toys, not shoes.