It's a blessing that the first Die Hard film even got made, let alone that it blossomed into a film-movie (and counting) action franchise that it is today. The original film began as an adaptation of the second book in a crime series – the first book of which was brought to the screen with Frank Sinatra starring. So Old Blue Eyes very nearly wore the vest.
The script wasn't finished when production began, director John McTiernan hated the project...it's truly miraculous it came out the platonic perfect action movie it is (what excuse does A Good Day To Die Hard have?) Since then, the ongoing adventures of John McClane and his multiple bad days have built their own rich, self-referential mythology.
In fact, it's an action movie series with a much stronger continuity than any other, with recurring villains, nods to the past and John McClane actually has a multi-film character arc. The ramshackle approach to producing them also means they're full of silly in-jokes, references to other films and Easter Eggs for fans that are really paying attention.
Obviously it's not quite the Marvel Cinematic Universe for densely packed references, but there's a surprising amount going on in the adventures of that bare-footed New York cowboy. From surprising cameos to crossovers to Tarantino nods, here are twelve Die Hard Easter Eggs you probably missed.