Film opens with "vintage" shot of little boy hiding behind Christmas tree. In walks drunk dad. Boy yells out "Santa!", dad drops glass, and says "I'm the only Santa you'll ever have kid."
Present day, Boyde is taking his son Douglas to see Santa. He laments when a wine-o Santa appears walking down the sidewalk as his son is about to talk to a "retail" Santa. The boy asks how there can be two Santas. Dad assures him Santa is real. Older sister Vera says something like, "But I heard from Mary's older sister - the one that gave the BJ to... " Dad chokes on coffee. Mom asks "Do you know what a BJ is? Sister says, "I think it's a but-jam, like someone jams something up your but." Dad regains composure and tells sister not to say anything that will ruin little brother's Christmas.
Cut to bedroom that night, Boyde is in bed with his wife Luann. He declines her overture for sex. Says "If we can just let little Douglas believe in Santa for one more year." Phone rings. It is Boyde's brother Nelson, who is putting a frozen burrito in a blender and feeding it to a baby. He asks Boyde to be godparent to his son, Boyde agrees. When he is told the baby will be Christened on Dec. 24. Boyde realizes he will have to spend Christmas with his family in Wisconsin.
Cut to hallway. Boyde has big box with little boy's present. Douglas boy comes in and Boyde ditches the present in side room. Motions to Luann, pointing to the present. She gives tumbs up. Boyde walks the boy upstairs.
Cut to drive to Wisconsin in white BMW SUV. Boyde is pulled over for speeding.
Cut to the Boyde homestead. Various "characters" from Boyde's family and arguing. Mitch, his dad, is upset because Boyde won't eat venison for Christmas even dinner. His mom, Donna, wants to find her camera. Says something like, "Help me find my GD camera." Boyde's sister Shuana is apparently still breastfeeding her son, and tells him "You have to wait for your milk until everyone else eats." The other children are in yard vandalizing Christmas lawn decorations with a golf club.
Boyde arrives in Wisconsin with family. They go through some shenanigans with the family. Boyde is upset when he discovers he has been fed squirrel. Boyde's nephew Rance stuffs himself with 10 dinner rolls in 30 seconds. The night progresses and the children are put to bed in the basement. Boyde comes upstairs and does the "Where's little Doug-ey's present?" routine. He decides to drive to Chicago and back to get the present before the boy wakes up.
Immediately his car breaks down. Mitch is dispatched to get him, in a 1980's vintage Custom Deluxe flatbed with a rack of port-o-potties on the back and a manual-on-the-column transmission. As they drive together to Chicago, the film cuts back and forth between the characters on the road and the characters at home. The brother-in-law talks about beer. Boyde and Mitch stop for gas. Luann and Donna talk about sex or lack thereof. Boyde and Mitch get another speeding ticket. Rance challenges Douglas to pickle eating contest with a really old jar of pickles they find on the canning shelf. Boyde finds his brother Nelson passed out in one of the port-o-potties. Boyde's sister blames her mom for her low self esteem as she massages her hustbands feet. Boyde and Mitch argue about the Christmas music on the radio, and why they don't get along.
Finally they arrive. Boyde forgot his keys. He breaks a window and finds the dog sitter in the house with his entire family. Some antics ensue, and while that is going on, Mitch sees a family picture he has been photo-shopped out of . Boyde calls wife, gets mad because the dog sitter doesn't speak English. Finally Boyde finds the present, and they hit the road back to Wisconsin. Mitch is sullen about the family picture. They argue. Cut back and forth to the people at home. Mom and wife go through the attic. Boyde outruns the (same) cop who tries to get him for doing 90 MPH again. Chase ends with him crashing into a port-o-potty. Mom and wife drink vodka. Boyde runs over a wine-o Santa. Kids wake up and start going through presents. Boyde and Mitch convince wine-o Santa to drive them the last 10 miles home on his vintage snowmobile (which sparks down the road, since there is no snow). They get home. Wine-o Santa gives the present to little Douglas. Douglas takes Santa's hand and says "I believe in you" or something to that effect. Douglas is unimpressed by Dad's present when he opens it, but is floored when he opens a vintage Bridge for Kids game that his mom found in the attic. Family goes outside for more shenanigans. Roll credits.