When Caroline's brother has the car, she tells him to pick her up at 2am and he complains that he has to get up for school. Then, when he fails to get her, Adam walks her home. She tells him that the next day is Christmas Eve, but kids in Minnesota do not have school on Christmas Eve.
When Caroline retrieves the third package of cigarettes for Howard from the vending machine, she has the first two packages in her left hand. She turns and walks over to Cindy to hand her the key to the machine, and the cigarettes in her left hand are gone.
When Caroline is getting ready to meet her boyfriend at the beginning of the movie, we see her sweep a bunch of makeup off of her dressing table and into her purse, then she walks off the screen to the right. When she comes back, the makeup is back on the dressing table.
When Caroline and Cindy are standing at the front counter refilling the salt and pepper shakers, when Caroline is talking about her Christmas plans, Cindy has a pen stuck in the right side of her ponytail. A few minutes later, as the two women walk to the back counter to start on the sugar jars, the pen has disappeared.
The scar shown on Adam's chest is on an angle, from top right to bottom left. Heart surgery requires the sternum to be split, leaving a 7-10 inch vertical scar from top center, just below the collar bone, to middle center, just above the abdomen.
When Caroline watches Adam put his sweater on he has nothing on underneath it. When she goes in to talk to him moments later, he has an undershirt sticking out from underneath the sweater, but as he was putting it on you could see he put both the sweater and undershirt on together.