Right before the musical number when Lily is shuffling backwards from Barney she can be seen wearing white striped socks. During the musical number she is wearing dark socks.
When Karina walk out and Barney starts singing her hair is totally different from when they were in his apartment.
During the musical sequence "Nothing Suits Me Like a Suit" when Barney climbs on top of the Taxicab, a crew trailer and small buildings that would not be located in Manhattan can be seen in the background