Curtis Arden receives an "introducing" credit
Due to a mishearing of the word "fuck" by the BBFC the 1995 video release was wrongly given a '12' certificate. This was corrected for the 2003 DVD and the rating changed to a 'U' certificate.
Gwangi is a native American word that means lizard.
In 1971, Warner Brothers cleverly reissued this film in the USA on a double bill with When Dinosaurs Ruled the Earth.
Leading lady Gila Golan was re-dubbed, but the voice actress remains unidentified.
Special effects master Ray Harryhausen has said that sequence of the elephant performing its act and its subsequent fight with Gwangi were done with no shots of a real elephant because no such animal was available. However, there is an elephant in the very early scene of the Wild West show's parade through the town, and Ray's animation puppet is a perfect double for it.
The roping of Gwangi was achieved by having the actors hold on to ropes tied to a "Monster stick" that was in the back of a Jeep. The jeep and stick when filmed with Gwangi are on a back rear projection plate and hidden by his body and the portions of rope attached to his body are painted wires that are matched with the real ropes.
The sound that Gwangi makes is that of a camel and a raspberry run backwards.
When this film was first conceived it was supposed to have been a follow-up to King Kong, but was never made. However, an early B&W version of the "cowboys in Africa" footage was shot, and wound up being used in Mighty Joe Young.