Among the most hated of the daikaiju movies, Great Monster Yongary is also the best known of the South Korean monster films. Although it's not the first one of its kind (that honor goes to the long-lost 1962 variant of Pulgasari), it's the first one in color (assuming the first one was in black and white) and the only movie given a dubbed North American release.
When released in South Korea, the movie wasn't well received, but it still got sent to American International to be dubbed and released across the world. The movie was, until recently, believed to have been heavily cut for the American release, but new evidence suggests only the original language print is partly lost. The Japanese edit ran at an hour and 14 minutes, while the original and now lost South Korean version was at an hour and twenty. The AI print also runs at an hour twenty, but is missing the original credits, and the dubbing ended up cutting out some dialog.
It seems that none of the alternate edits of the movie still exist, the only restoration done to the AI edit revolved around the credits. There is still a 48 minute long fragment existing of the original version, but it is heavily cut and contains no previously unseen footage.
Also of note is the 1999 remake of the movie, simply called Yongarry.
The first version of the movie did so badly that the DVD release literally never sold, and the movie was pulled from the shelves and reworked for a 2001 release. There is a little known about the changes, but still more than what we have for the 1967 original film.
Another South Korean monster film, Youngster Gugu and Monster Zuzu has a monster with a similar design and even has an alternate title of Yongary Raids Again.
The IMDB page for the movie.
An article about Yongary Raids Again Retrieved Nov 8th, 2013
An article about the movie in question Retrieved Oct 23, 2013