Revealing mistake: When Doug and Deacon are driving round trying to find Gabe's Pizzeria, they get into the car and pull out into the road. However if you look at the traffic, they would have hit at least 2 cars in doing so. But they don't, showing it's a projection.
Continuity mistake: In the kitchen when Arthur says he was a terrible father and gets up, Holly looks over at him with her hand on the edge of the table. She says, "Oh no", but then she's smiling. When the shot changes angle, her arms are crossed. Then Holly says, "Better than my dad, who was too busy chasing the almighty bottle of glue", her hand is instantly on the box of photos again.
Continuity mistake: In front shots of the house you see that the garage is in the front and opens to the street, but the garage door is behind the house entirely. It seems to open in a back alley or private entrance way. The way it is shown in establishing shots, it can not be open to the front street at the front of the house.