Four noted Canadian film directors make cameo appearances in the film. We see Atom Egoyan as a director of O'Malley of the North, Ted Kotcheff as the conductor on the train, David Cronenberg as another of O'Malley's directors, and Denys Arcand as the head waiter at the Ritz. And, although better known for their acting, Paul Gross and Saul Rubinek are also movie directors.
When Barney is meeting with Miriam for lunch he grabs the waiter's jacket and asks for "Beluga." When he does this he grabs low where the jacket overlaps. When the shot changes it has him holding the jacket higher up.
After Boogie is caught with The 2nd Mrs. P, she leaves and he sits on the stairs wrapped in a blanket, talking and sharing a drink with Barney. When Boogie gets up to go to the kitchen to get more booze, the blanket falls on the floor in the hallway. When Boogie comes back with his drink, the blanket is back on the stairs.
In Rome many of the road signs are clearly from today. The two small format ones at the corner of Via Condotti and Piazza di Spagna are an example. Also the out of focus no parking signs on the doors of many buildings are clearly of the most recent kind.