Despite playing a tough guy in the movie (and having a tough guy image in general), Dwayne Johnson admitted that he felt nauseous after playing the original Doom game.
The character of Sarge (played by Dwayne Johnson) is an homage to Master Sergeant Thomas Kelly, one of the main characters from the video game Doom³ (2004).
Rosamund Pike turned down the role of Rita Skeeter in Harry Potter and the Goblet of Fire (2005) to work on both this movie and Pride & Prejudice (2005).
No Marine would ever refer to a sergeant of any rank as simply "Sarge." This is only done in the Army and the Air Force. However, this could be because it is the Sergeant's "battlefield nickname", considering several other members of the squad are also called by nicknames.
When the Monster grabs Pinky, Reaper and Sarge go after it. When they round the corner, they fire their weapons through a Nano-Wall at the monster. However, in the next scene, the Nano-Wall disappears, then re-appears when the horde of zombies arrive.
Sarge being called Sarge implies that he is obviously ranked a Sergeant. During the film Reaper addresses Sarge as 'sir'. In all military services Sergeants are Non-commissioned officers and are only allowed to be addressed as sergeant not sir.
What are the differences between the theatrical version and the unrated version?
A
In comparison with the R-rated theatrical cut, the unrated version runs more than 6 minutes longer adding more action and story to the film.
A detailed comparison between the theatrical version and the unrated version can be found here.
Q
Are there Demons/Hellspawn?
A
Whilst some of the creatures in the film look like their counter-parts, in Doom 3, there is no direct reference to Hell or alternative dimensions. The creatures were explained to be genetically mutated humans, due to an injection of a 24th Chromosome. Although in the cast listing it does show an actor listed as a "Hellknight" which were the names of the creatures in Doom 3