Will Ferrell stated this is his favorite of his films, for sentimental reasons- throughout the span of the shoot, his wife became pregnant with, and gave birth to, their first son. He said he filmed specifically imagining watching the movie with his child one day.
When Phil & Buck are in the basement playing darts, Buck throws a bullseye, then pulls his darts from the board, thus leaving the board free of darts. Phil's first ensuing throw lands in the neon sign, breaking it. Buck throws his dart and lands a bullseye, but there are two other darts in the bullseye circle in the close-up.
When Umberto agrees to let Gian Piero and Massimo play soccer, Maria (the woman next to Umberto) claps her hands and looks at the kids. In the next shot, she has a Sharpie pen in her hand and is in a completely different position.
When Phil and Buck are making their bet, the Pele ball is seen on the fireplace mantel in the living room. Earlier in the film, the ball is shown in Buck's study.