- Missing Episode: When American International Pictures bought the rights to redub and distribute it in the US, the Korean producers shipped all the original film stock and negatives to AIP, rather than copies. Now, the Korean version of the film is believed completely lost.
- What Could Have Been: Yongary was originally conceived as a single celled organism that came from space and was mutated by radiation.
- The remake was originally going to use traditional suits for the kaiju but it was replaced with CGI. Stills of the suits can still be found, and most people agree they look much better than the CGI.
- In some behind the scenes photos for the remake, there are maquettes for what look to be a two unused Kaiju. One of them slightly resembling an upright standing version of 1998 Godzilla (sans dorsal plates), and the other having a draconic appearance and two absolutely massive wings. Weather these two monsters were prototypes for the new Yongary and/or his opponent Cykor, or evidence of an ultimately scrapped sequel is anyones guess.
Trivia / Yongary: Monster from the Deep