In fiction, a MacGuffin (sometimes McGuffin) is an object, device, or event that is necessary to the plot and the motivation of the characters, but insignificant, unimportant, or irrelevant in itself. The term was originated by Angus MacPhail for film, adopted by Alfred Hitchcock, and later extended to a similar device in other fiction. (Wikipedia)

Die Hard (1988) Review
It’s Beginning to Look a Lot Like Christmas Die Hard (1988): 10 out of 10: Bruce Willis (Yes, the guy from the wine cooler commercials) […]