Attack of the Monsters at least comes from a period when the Gamera series had taken on a colourful silliness. (This was something that also infected many of the Godzilla entries from the same era). The planet Terra is depicted with a wonderfully pulpish colour like an alien world out of some of the better 1950s science-fiction films. The guest monsters are among two of the most absurd ever created on screen – Gyaos is like a giant flying bat with an axe-shaped head and a tail taken from a 747; while Guiron looks like an ambulatory walking shark with a snout shaped like a meat cleaver. The battle between the two of them is immensely entertaining – with Guiron chopping Gyaos’s leg off with his bladed nose and Gyaos bleeding in great purple-blooded chunks. The battles become even more lunatic once Gamera enters the scene – Guiron batters Gamera’s turtle shell with his bladed beak causing Gamera to splatter gouts of green blood; Gamera grabs Guiron in an airplane spin and throws him to impale him in a rock, nose first; Guiron fires deadly shuriken from his nose; Gamera tries to heal his wounds by piling ice against his epidermis; Gamera makes leaps about 100 feet into the air and comes down on Guiron’s back; Gamera grabs onto a strut that connects two towers and swings around and around it like a gymnast doing loops on the bar; and Gamera finally tosses a missile and impales it through Guiron’s shuriken missile nasal vent, blowing him up and causing his severed head to go flying up into the air.

The effects are about average for the era and somewhat uneven – the flying model of Gamera is immobile and has cartoonish eyes – but the sheer colour of the fight scenes makes up for this. Attack of the Monsters also borrows the name of the intergalactic heroine from the previous year’s tongue-in-cheek space opera Barbarella (1968), naming one of its female alien invaders Barbella.

The other Gamera films are:– Gammera the Invincible (1965), Gamera vs Barugon/War of the Monsters (1966), Gamera vs Gyaos/Return of the Giant Monsters (1967), Destroy All Planets (1968), Gamera vs Jiger/Gamera vs Monster X/Monsters Invade Expo 70 (1970), Gamera vs Zigra (1971) and Gamera: Super Monster (1980). The series was revived in the 1990s with Gamera, The Guardian of the Universe (1995), Gamera 2: Assault of Legion (1996), Gamera 3: Revenge of Iris (1999) and Gamera the Brave (2006).
 

Trailer here:-

Full film available online here:-