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.
While on his honeymoon with the second Mrs. P. Barney is sitting on the bed reading a newspaper. During his conversation his right leg is outside of the bedspread. When he says he is going to take a quick nap his leg is still showing, but as he is speaking he swings the newspaper with his left arm. The camera angle changes and his leg is now under the cover as he finishes swinging the paper.
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.
On the radio Miriam introduces the song "I Don't Want to Hear It Anymore" by Dusty Springfield. The recording played is the version by Shelby Lynne which was recorded in 2008.
It is not possible for a swimmer to be scooped up by a firefighting airplane.
Miriam places a stone on Barney's gravestone overlooking downtown Montreal. Barney bought a plot in the Mount Royal Cemetery which is on the north side of Mount Royal while the city is on the south side and so not visible from the grave site.
When Barney and his son are fishing, a taut rope can clearly be seen stretching out of frame from the bow of their boat (as though it is anchored to a dock).
When Barney flips out because he cannot remember Miriam'a telephone number he grabs the bottle, which is obviously a break away prop, with such force that the bottle breaks while he is still lifting it upward.
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.
The TV studio cameras shown in the latter part of the film, time assumed as probably the 1980's, were modern ped, CCD cameras. Real cameras in their day would have been old plumbicon cameras, which were bulkier. The lenses too were not of their time, they are too modern.
During Blair's discussion of the future of veganism over dinner he ponders whether one should say "in less than 50 years" or "in fewer than 50 years". He incorrectly settles on "fewer" reasoning that you're counting years and not measuring time. A ten-year calendar has fewer than 50 years on it, but something that will come to pass sooner than 50 years from now will do so in less than 50 years.
Izzy is wearing a "Chai" necklace "inside out" so the viewer is seeing the back side of the Hebrew letters.