Just after Margaret and Andrew bump into each other after she comes out of the shower, we see Andrew stepping out of the bathroom to talk about the dog. When the scene cuts, he is seen stepping out of the bathroom again.
After Andrew announces his engagement to Margaret to the guests, a woman's voice is heard saying, "Let's get some champagne." Later in the same scene, after Andrew and Margaret share their long kiss, the same voice can be heard saying the same line, even though everyone in the shot is already holding a champagne glass with liquid in it.
When Margaret is telling Andrew's family and friends about how they got engaged she says that the two were celebrating their one year anniversary. When the government official comes to Alaska, Andrew tells him that that "six months ago we started dating, we fell in love".
When Margaret and Andrew are talking outside on the street after first leaving the immigration office you see a FedEx truck in the background behind Andrew on the street. As the scene switches between the two of them it disappears and then instantly reappears.
When Andrew and Margaret first go into the immigration office, Mr. Gilbertson is reviewing Margaret's case in a plain manila envelope. When he tells them that he will see them on Monday and tosses the file, it is now a much darker folder.
While Andrew is at the door of the chairman's office the camera switches between him and Margaret with the chairman in the background. Originally the chairman was sitting with legs under the desk then he was turned out with one leg on the other and then he was back in his original position again.
When Margaret and Andrew first arrive at his home, Margaret pulls Andrew aside during the party by grabbing the front of his jacket. When the scene switches, she is holding onto the sleeve of his jacket.
In the scene at Federal Plaza when the camera is on Andrew an Asian woman walks past him in the direction of Margaret. In the next scene the camera is on Margaret and we should see the Asian woman but she is not there.
When Margaret, Andrew, Gammie Annie and Grace arrive at the boat dock, Margaret asks Andrew if she shouldn't be checking into their hotel room. Grace says she has canceled the reservation and that "family" doesn't stay in a hotel. At this point Andrew and Margaret's engagement hasn't been announced so Margaret isn't family yet.
A time-lapse scene shows the sun not setting during the night at Sitka. Alaska is almost 1500 miles north to south. While there are places in Alaska, above the Arctic Circle, where the sun doesn't set at night in summer, the sun always sets in Sitka, even in summer (though sometimes quite late, and nautical twilight isn't reached every night).
When Margaret and Andrew are in her office, a view out the window shows the barren trees in the courtyard (flimed at International Place in Boston in late winter/very early spring) but yet the same weekend they are in in Alaska where everything is lush green, even though Alaskan Spring is far behind Boston and NY Spring.
When Andrew and Margaret are speeding at the buoy and Andrew turns the boat hard to the left, Margaret falls out of the boat to the left. If the boat is turned hard to the left, the natural reaction would have been for Margaret to be thrown to the right. It's Newton's Third Law of Motion.
After Andrew and Margret bump into each other, after they've covered themselves up Andrew says 'nice tattoo by the way' but when you watch the scene there is no way he would have been able to see it as he never sees the back of her in that scene.
Granny Annie, who is celebrating her 90th birthday says she wore the wedding dress when she was pregnant, but also says her mother made the dress in 1929. Granny would have been ten years old in 1929, however, Granny never says that she was the first one to wear the dress.
The goof items below may give away important plot points.
Before leaving for Sitka, Mr. Gilbertson schedules an 11am appointment for Monday. When in Sitka, Andrew and Margaret stay three nights, indicating that they have stayed through Monday. Although the immigration official arrives in Sitka on what would be Sunday, there is no mention of what day it is in reference to when Andrew and Margaret would get back to their lives.
When Ryan Reynolds' character is reading her letter after she runs away from the wedding, you see the wedding dress in the background. In the first scene, the necklace from Grandma Annie isn't there, in the second scene, it is, and the third it is gone again.
A day before the wedding, right after Andrew and Margaret meet Mr. Gilbertson in the Paxton family's barn, they are seen in their bedroom, and suddenly, Grandma Annie walks in, taking the baby-maker from the bed and telling them that they are to sleep separately tonight. The camera does a full perspective showing Grandma Annie leaving the room, and when the camera focuses back to Andrew, Grandma Annie is seen in the background leaving the room again.
In the scene where Margaret gets in the boat and roars away, after they get out in the open water you can plainly see that they had just started the boat up and had not been going full speed the whole time.