There's one part in the song, "Master Of Puppets," When James Hetfield shouts, "Pancakes!" before Kirk Hammett comes in with his solo. The original lyric is supposedly be, "Fix me!" however, "Pancakes" was an inside joke that came from the former bassist, the late Cliff Burton. When Metallica was on tour with Anthrax in 1986, Cliff was asked by Anthrax drummer Charlie Benante, what was James shouting. Cliff casually answered, "Pancakes."
The trivia item below may give away important plot points.
Some speculate that since drummer Lars Ulrich is a huge fan of Quentin Tarantino, the bag the roadie was sent to recover, contained late bassist Cliff Burton's soul. Hence the ending credits where the band was playing Cliff's swansong "Orion."