The health and detection boxes originally had no icons, and were simply unlabeled bars.

The anaesthetic weapon, which can be used to non-lethally incapacitate enemies, originally had a different appearance. It was originally depicted as a jar with a rag, and Agent 47 would have presumably used the chemical-soaked rag to knock out enemies. It was replaced with a hypodermic needle in the final game.

During the mission "Invitation to a Party", the newspaper located in the offices says "FCK Danish Champions 2001". This is a reference to the Danish Copenhagen soccer team FC København, who won the Danish soccer tournament in 2001. The smaller headline reads "FC København beats Bundby". Bundby is actually a town called Brøndby, the wrong name is simply a joke from the developers. "Bundby" translates to "Bottom City" while "Brøndby" means "Well City".