In the World Premiere Uncut Trailer, at 1:19, when Frank Woods throws Alex Mason the SPAS-12, it makes the sound of the magazine being loaded into a TAR-21. This sound is different in the final version of the game.
The Defector was originally named "Slaughterhouse" during early development.
The real Defector can be found laying on a desk in the same room where Reznov is found. Jason Hudson later reveals that he was killed during the fighting.
The fact that Reznov is really Mason's imagination is hinted at when Reznov introduces himself to the SOG Team, Woods just asks Mason if he's retrieved the intel. Adding to this is the fact that Reznov's missing finger is now present.
Most of the Marines seen on the sides of the street before Mason gets the radio from Crosby don't have name icons on them.
When Woods uses the SPAS-12 on the NVA soldiers, it uses normal ammunition. This is because Mason has the incendiary ammunition, like Woods points out a few seconds later.
There is a peace symbol painted on the wall where Bottom Feeder is destroyed.
During this level, Reznov uses a Commando. However, during a flashback of this level during "Revelations", Reznov is holding an AK-47, which cannot be found anywhere during The Defector.
It appears that the level originally was to have the North Vietnamese Army use the AK-47 as their main weapon, as seen in the trailers and screenshots of Call of Duty: Black Ops, but was later changed to the FN FAL.
If the player follows the first civilian seen in the level, he will run all the way to the first room where the player crashed through the window, at which point a grenade will explode in mid-air, always killing the civilian.
After taking the radio from Crosby and following him, Crosby will be firing support from behind. But after killing all the enemies, he will randomly die, even though there were no enemies alive to kill him.
After crashing through the window at the start of the mission, if the player turns around and looks out the window where the crashed Huey should be, there is just an empty street.
When Woods tosses the SPAS-12 to Mason, the latter's hands clip through the handguard.
At the start of the level, to the left of Woods, there is a Commando with several attachments on it, which is visible when Woods shoots the NVA soldiers with the SPAS-12. It appears to have an Infrared Scope, Masterkey, Suppressor and Extended Mags. However, when Woods tosses the SPAS-12 to Mason and then picks the Commando up, the attachments have disappeared.
The front turret of RT Texas has 'Say Cheese!' painted on it.
If one shoots the first encountered civilian with the Dragon's Breath, he will not burst into flames like usual.
The FN FALs and SPAS-12s that the North Vietnamese drop will sometimes have ERDL camouflage.
The NVA loudspeaker throughout the level isn't even speaking Vietnamese at all; just random gibberish.
If the player noclips up to RT Texas before it is driven off by the ZSU, it will have several troops sitting inside. These troops have Commandos with overlapping attachments, similar to the one at the start of the level before Woods picks it up.
The player can actually see the tank spawn out of nowhere in the road when going over to it.
The projector screen seen when Mason meets Reznov references several later missions, including Mt. Yamantau, the Rusalka and Rebirth Island.
A clock in the hallway, before encountering Reznov, shows that it was 3:00 PM, although the briefing states that the mission occured at 1900 H (7:00 PM)
After Woods shoots the NVA soldiers at the very beginning of the game, the weapons they drop will disappear.
Some of the watermelons in this level cannot be exploded by gun fire like they usually do.
When taking the radio from Crosby, Mason will say "Pull it together and give me that radio!". However in the captions, he will say "Hey! Give me that radio!".
After the player takes the radio from Crosby, they may hear Reznov say "It is good to fight by your side once more!", this is also what Dimitri Petrenko says to Reznov during Project Nova after the player starts the assault on the Nazi base.
The player may also hear Reznov say "Rain Fire!" which is Step 3 to the escape of Vorkuta.