When Claudia is saying goodbye to her daughter in the car outside the Chicago airport, all the cars driving by have Maryland plates because the shot was actually filmed at BWI in Maryland.
When Claudia goes into the basement to talk to her sister, her lipstick is on/off between shots.
At the dinner table, after the turkey drips down Joann's face, her bangs are soaked then dry, then soaked again.
The pile of Reddi-Whip on Henry's pie the night Clyde arrives changes height between shots.
When entire family is at dinner table, Aunt Gladdy is asleep, then passing food, then asleep again.
When Russell has finished fixing the family's furnace, he turned to Tommy and said, "How about those Panthers?". Since this film is set in Baltimore, this would be considered an odd statement, even by Tommy. The city had lost the Colts and the film was released a year before Baltimore obtained the Ravens. Baltimoreans wouldn't have rooted for a team in North Carolina. "Redskins" would have been more appropriate.
Knife sharpener and knife held by Tommy as he carves turkey are mistaken for a rod prop that propels turkey on to Joanne's lap.
When entire family is at dinner table, you can see the rod used to launch the turkey onto Joann.
At one point, Tommy mentions that it's the last chance for Jack in the Box, and then lists some Jack in the Box menu items. The closest any Jack in the Box has been to Baltimore is in North Carolina.
When Tommy and Leo are peaking into the house with the night vision goggles, you can hear Tommy say "come on" even though his mouth does not move.
When Tommy Larsen is on Leo Fish's shoulders changing the light bulb on the porch at Aunt Gladys's house, they fall over and the blue mat they land on pops up and remains visible.
Tommy tells Claudia that it's the "last chance for Jack In The Box," which doesn't have locations in Baltimore.
Although Claudia lives in Chicago, the shots in the museum she works in and shot of the museum steps she descends at the beginning of the film are actually shots from the Baltimore Museum of Art.
When Claudia's daughter drops her off at the airport, the distinctive red tiled pillars let the viewer know that the airport is not one located in/around Chicago, but rather is the Baltimore Washington International airport (BWI).
Adele refers to a troop of Cub Scouts. Cub Scouts come in packs, not troops.