Accidentally Accurate: Some have questioned the credibility of the fact that Captain Englehorn is able to translate the language of the islanders, who have apparently never had Western visitors before. He describes it as similar to the language of the Nias islanders. Nias is a real place in Indonesia, but the language of the film is completely fabricated. Nonetheless, Englehorn's ability to translate is not all that implausible; most of the languages of the Pacific share common enough roots to be mutually intelligible to fluent speakers.
What Could Have Been: At one time in the 1933 film there was a scene when the crew of the venture fall into a pit that is filled with giant spiders and insects that soon devour everyone. However, the filmmakers felt that the spider pit scene would slow the film down, (not becuase the scene was too shocking, as is commonly reported) so they had to remove it. That scene would later make it into the 2005 remake, and recreated by Peter Jackson on the 2005 2-Disc DVD set.
Fay Wray was also going to be the one to deliver the "It was beauty killed the beast" line at the end of the 2005 remake. She refused, at first, but then considered the possibility. However, after her meeting with Peter Jackson, she suddenly became ill and died a year before the remake was released. As a result, the line ultimately went to Jack Black's Carl Denham character as an homage to the original, while a brief mention of her (and Merian C. Cooper) was featured at the beginning as a Shout-Out.
Also, there was another draft of the script that came out in 1996, which was different from the 2005 remake, described as a "tongue-in-cheek comedic film with elements of Raiders of the Lost Ark and other films". However, Jackson didn't like that draft a bit, and he was glad that Universal Films pulled the plug on that film version, as he was able to write something better.
Peter Cullen voiced King Kong in the 1976 version (but was uncredited). Sessions apparently got so intense he coughed up blood at one stage, and because of said experience he nearly refused to voice Predator.
There's a deleted scene from the 2005 remake, in which the first time they hear King Kong's roar is after he's heard an acting scream by Ann while Denham's filming. This was put into the game.
There's also an Ascended Extra for the game; Hayes stays alive much longer, and when he eventually dies it's by getting trampled by a T-Rex.
What Could Have Been: The 2005 remake was originally scored by Howard Shore, but it was later removed from the film when Shore and Jackson agreed it didn't quite fit (hence James Newton Howard having to do a rescore at a very late stage - that's why three conductors and a small army of orchestrators are credited). Shore had already filmed his cameo as the orchestra conductor, however, and it remained in the movie.