Fridge Brilliance
- How does John know that "Bill Clay" is Hans? Several things clue him in:
- John glances at a directory board behind Hans and notices that Bill Clay works on the 29th floor. Earlier when John arrived at Nakatomi, the guard at the desk told him the only people left in the building worked on the 30th floor.
- Except the people on the 30th floor are there for a Christmas party. There's no reason to assume that only the folks from that floor were invited.
- Hans holds a cigarette in the European style (held with the thumb and pointer finger) instead of in the American style (between the pointer and middle fingers).
- "Bill Clay"'s accent is very neutral, which John thinks is either forced or unnatural.
- Hans is found near the roof, with the excuse that he escaped the terrorists and wanted to signal for help from the roof, somehow escaping armed terrorists that held everyone at gunpoint on the 30th floor. Him being found under the rooftop helipad and jumping down from the ventilation systems also was suspicious.
- According to the screenwriter, John was supposed to notice that all of the robbers he comes across have the same watch. However, the scene that introduces this fact had to be cut because one of the shots reveals that their truck does not contain an ambulance (which was written into the movie after this scene was filmed). If you look very closely, you can see that the terrorists all have the same watch, and notice that John reacts to Hans' watch when he takes a cigarette, but it's never actually explained in the finished film.
- Last but not least, John saw Hans from above in the elevator. He hasn't changed his clothes, hair, or body type in the intervening hours, so it wouldn't be hard to identify him, even if he didn't get a good look at his face.
- Alan Rickman also has a very distinctive voice. Even putting on a phony accent, it's still clearly the same person John saw talking in the elevator. He may have had a suspicion from the moment he met 'Bill Clay' as a result, and simply wasn't certain until later.
- Maybe he didn't know for sure, so he gave "Bill" a unloaded gun to see if he tried to shoot him with it or not.
- John glances at a directory board behind Hans and notices that Bill Clay works on the 29th floor. Earlier when John arrived at Nakatomi, the guard at the desk told him the only people left in the building worked on the 30th floor.
- Had John not ignited his lighter in the vent shaft after falling, Karl and the other terrorists most likely would have assumed he fell to his death (Karl hears the noises of him falling down the main shaft), and he would have had some breathing room to move around.
- The Throw It In! where one of the terrorists positions himself in a concession stand to assemble his weapons, and help himself to some candy. It's funny that he looks around to make sure nobody's watching first, as if nicking a Nestle Crunch is what he's worried about people seeing. But then you realize, the cops are literally about to come through the door he's supposed to be watching, and the last thing any of them wants is to have one of their guys too busy munching on a chocolate bar to shoot back.
- Gruber sees the model of the bridge outside Takagi's office and comments how he loved to put together models as a boy with adherence to exact details. This later is referred to when he says they planned for every conceivable scenario. Guess an estranged cop husband being at the party was inconceivable.McClane: I got invited to the Christmas party by mistake. Who knew?
- The fight between Holly and John at the start of the film causes Holly to put down her family photo, which ironically keeps her husband's identity a secret long enough to shake things up and very satisfyingly sets up the climax.
- The bad guys are German, and "Ode to Joy" is a German song.
- CinemaSins points out how suspicious it would be if Hans' crew supposed to get out of the building from a locked garage in an ambulance, but the whole plan actually works out, once the roof blows, the police fire department would assume everyone is dead and open up the garage bringing in paramedics and ambulances to help the survivors/bag bodies, therefore enabling the crew to get out by blending in plain sight.
- A bit of Fridge Horror: Hans and company took everything into account with the exception of John being at the building. Picture how things would have played out had he decided not to come to L.A., miss his plane, or had it been delayed. Hans and his crew would have succeeded and everyone at the party, Holly included, would be dead.
