You can see the prep school photo of Tony taped to the corner of Ziva's computer screen in the scene where she and McGee are discussing Tony and his father's relationship
This is the first episode where you see DiNozzos apartment
Tony's goldfish is named Kate. Presumably, after Agent Kate Todd.
Several characters have seasonal names to fit the Christmas episode such as Noel and Winter.
The uncirculated $100 has the Liberty Bell on the wrong side of the Franklin portrait. The $100 bill was of a early batch of a new design. Not unreasonable to believe that the layout was changed from current $100 bills.