It's a children's kaijuu film and the fourth in its series. Gamera is the kind of city-stomping monster whose hobbies include attacking spaceships. Normally you'd expect him to be fighting Godzilla to the death, but that's impossible because Godzilla's owned by Toho Studios while Gamera belongs to Daiei.
He's a turtle. He's about 70m long, weighs 1000 tons and can fly at Mach 3 by shooting flames from his legs. However he's also a Friend Of All Children. The early Gamera films had been less kiddie-oriented, but this is the fourth film in the series and by now we have:
(a) prankster child protagonists
(b) jolly comedy music and a theme song sung by children
(c) Gamera telepathically knowing what children want him to do, like a large, prehistoric Lassie. (It's possible that he'd heard and understood what they were shouting, but frankly I find telepathy more plausible.)
Also, this film was being made with an eye to US distribution, so the producers were following American TV broadcasting standards. This makes it even tamer than you'd expect from a cheesy kiddie film. Well, except for the decapitations. Tomoko and I fell about laughing at that scene, since it's so unexpected. (No gore, mind you, and it's actually just aliens doing something alien to their fellow aliens.)
Other American-pleasing additions include some American cast members, including one of the two child heroes (Masao and Jim). The distributors insisted. You can tell that Jim's American because he can throw lassos like a cowboy, which never looks convincing. Fortunately though all Western actors have either been dubbed (the adults) or can actually speak Japanese (Jim). The child actors are good, in fact.
The film also has separate Japanese and American cuts, with the latter being a good twenty minutes longer. (That was another distributor requirement.) I believe the extra material was all recycled footage, which boggles the mind a bit since even the shorter Japanese cut I watched nicks entire sequences from earlier films in the series. These are easy to spot, especially the one in monochrome. (D'oh.)
Is it a good film? Goodness me, no. Is it entertaining? At times, yes, riotously. I was in danger of doing to sleep about halfway through, but at other times there's enough lunacy to keep an adult audience laughing their heads off. Thus I actually rate it higher than a lot of more straight-laced monster flicks, which can be just as bad (or worse) but have less entertainment value. Things that made Tomoko and me laugh include:
(d) the bleeding-heart U.N. Aliens have kidnapped Masao and Jim and have promised to kill these two boys unless the Earth surrenders! Hmmmm. Let me think about this. Two boys vs. the entire planet. I know what I'd choose. Even the boys themselves tell their friends and family to attack... but the U.N. can't bring themselves to kill two children and agree to surrender! (The aliens then order the death of everyone on Earth.)
(e) the comedy gullible aliens. Masao and Jim escape from their bonds and want to vandalise the spaceship's control systems, but unfortunately the aliens are standing in front of the console! What should they do? Answer: run up and tell them that something's gone wrong with their Gamera-hypnosis beam! The aliens will believe you, see nothing suspicious in the fact that you're on the loose and hurry off!
(f) some of the Gamera special effects, especially his eyes and the impaling in the climactic battle. That was hilarious.
(g) "That's the end of Viras!" What? Come off it. All he did was fall underwater. And he's a squid.
(h) You've saved the Earth, but it's no dinner for you!
(i) "That's Gamera! He's a friend of all children!"
(j) The aliens watching a flashback sequence and concluding from it that Gamera "has unusual destructive powers" that hadn't been in the flashback sequence.
(k) The bit where Gamera has been immobilised by a Gamera-paralysing ray, trapping him in an energy bubble. Unfortunately Masao and Jim are in there with him and they don't have enough air. Can Gamera rescue them? Yes, he can... by lifting up the barrier with his flipper so that their mini-sub can swim underneath. No, really. I couldn't believe it. This appears to be a rubber force field.
This film was made on the cheap, even compared with earlier Gamera films. #1 was a feature film, #2-3 were made for TV and #4 onwards were made partly for US distribution. That said, though, the special effects are actually decent, considering. Cheesy, but effective. There's a good composite of Masao and Jim in the same shot as Gamera, although admittedly it's followed immediately afterwards by a much worse one. Similarly the mandatory final battle between Gamera and a giant alien squid hits the desired wrestlemania spot, although Tomoko thought Viras didn't destroy enough buildings.
I also quite like the aliens. Their gymnastic way of entering rooms is a nifty throwaway, while their occasional Sinister Glowing Eyes work quite well.
It's blatantly a children's film. It has a scene where adults entrust Masao and Jim with fixing a submarine, then much later another in which Masao and Jim rewire alien mind control technology that they've never seen before. They must be geniuses. There's also a Playing Pranks In A Mini-Sub scene, complete with comedy music. Oh, and using the lasso to get out of those bonds makes absolutely no sense. The plot is dribble. However I think it's quite successful as 72 minutes of entertainment, since it only occasionally made me sleepy and often made me laugh. It exceeded expectations, in a number of ways.