
Continuity mistake: After he climbs out of the air duct, John McClane's shirt goes from white to green. The dirt and grime from the air duct would cause discolouration only where the shirt comes in contact with the duct. However, his shirt is uniformly green including places that wouldn't make contact and it is impossible for all surfaces to make contact even in small areas. (00:23:05 - 00:56:30)






Answer: Most large companies, particularly hi-tech or multinational ones, require visitors to check-in, especially afterhours. By having John search for Holly's name, it can be verified that he actually knows someone who works there, that there is an actual employee with that name, and otherwise assess whether John is a legitimate visitor. This scene's real purpose, however, is for plot exposition. John learns from the monitor that Holly now goes by her maiden name (Gennero) rather than her married surname. We see John's annoyed reaction to learning this, which sets up a later confrontation between him and Holly over their troubled marriage.
raywest ★