->''"This is the film most baby-boomers saw in U.S. movie theaters and on TV. Fans had to rely on badly cropped VHS and DVD bootleg copies to enjoy the film thereafter."''
-->-- Loving script from the back of the first U.S. DVD release

''Godzilla vs. Megalon'' (''Gojira tai Megaro'') was the 13th entry in the Franchise/{{Godzilla}} series. It was the first film in the series to have someone other than veteran suit performer Creator/HaruoNakajima in the role of Big G, with Shinji Takagi taking over the rubber suit. Interestingly enough, this wasn't going to be a Godzilla film. To cash in on the [[Franchise/UltraSeries Kyodai Hero]] craze, Toho held a contest in 1972 to make a tokusatsu hero that would appear in its own film. The winning entry was from an elementary student, who called his creation "Red Arone". Toho changed the name to Jet Jaguar, and he was set to star in ''Jet Jaguar vs. Megalon'', but, unfortunately, was found not to be able to carry the film. Tomoyuki Tanaka suggested adding Godzilla and Gigan to the film. In order to make up lost time, the film was shot in three weeks and, all in all, production time lasted six months. The film bombed at the Japanese box office, and Jet Jaguar didn't get the intended series.

For everything its predecessor did wrong, ''Godzilla vs. Megalon'' did it that much worse. Stock footage abounded, the special effects were dodgy at their zenith, and much of the plot was contrived. Nevertheless, the film was the subject of a heavy marketing push, and saw decent theatrical success in the United States, where it was released to cash in on the success of ''Film/KingKong1976''. Megalon was nevertheless well-liked, and a series of video games redeemed Jet Jaguar in the eyes of many fans.

The plot centers around the conflict between an undersea civilization known as Seatopia. Nuclear testing has severely impacted their people, and as revenge against the surface people, they plot to unleash the wrath of their god, Megalon. The Seatopians set up a base by drying out a lake where our ostensible human protagonists, an "inventor" named Goro Ibuki, Goro's younger brother Rokuro and their friend Hiroshi Jinkawa, are trying to relax. They [[DullSurprise don't take it well.]]

The Seatopians attempt to steal Jet Jaguar, a prototype robot, from the inventors. The first attempt, while the robot is still incomplete, is [[HilarityEnsues less than successful]], but the second time sees them capture not only the robot but the three humans. The brothers are sent to be offed, while Jet Jaguar is turned against Japan and used to direct Megalon towards Tokyo.

The heroes escape from the clutches of the Seatopians, and after meeting up with [[RedshirtArmy the always hapless JSDF]], manage to regain control of Jet Jaguar and decide [[GodzillaThreshold to call in Godzilla]] to combat Megalon.

With the guidance of Jet Jaguar removed, Megalon is reduced to flailing around and stomping on a few redshirts. Upon [[OhCrap learning of Jet Jaguar's recapture]], the Seatopians send out a distress call to [[Film/GodzillaVsGigan the Nebula M aliens]], requesting Gigan's assistance, which in ''no way'' is an excuse to rely overly on stock footage, no sir.

Jet Jaguar [[{{Sizeshifter}} grows to]] [[HumongousMecha Kaiju size]] and teams up with Godzilla to fight Megalon and Gigan. Much silliness ensues, including the [[SarcasmMode awe-inspiring]] tail-slide dropkick from Godzilla to Megalon. Eventually, the two villains are repelled and Godzilla shares a victory handshake with Jet Jaguar, who shrinks back down to rejoin his creators. Godzilla, meanwhile, returns to Monster Island, ready for the next adventure...

For the ''Series/MysteryScienceTheater3000'' episode see [[Recap/MysteryScienceTheater3000S02E12GodzillaVsMegalon here]].

!!Godzilla vs. Megalon provides examples of the following tropes:

* AIIsACrapshoot: Subverted by Jet Jaguar. He is content to be controlled like any robot - until danger is about, at which he becomes a BigDamnHero and takes control of himself.
* AntiVillain: The Seatopians, and by extension Megalon. Their bizarre decision to send Megalon to attack ''Japan'' for nuclear weapons testing (!) aside, you can't help but feel they're a ''little'' entitled to be ticked at the surface world routinely exploding nukes, threatening their underground civilization with constant earthquakes.
* ArtisticLicenseHistory: About the [[EenieMeenieMinyMoai Easter Island Statues]] in the InfoDump, one of the main characters states they are 3 million years old ([[FacePalm huh boy]]....).
* BigDamPlot: Megalon destroys the Ogouchi Dam in the film's most elaborate set piece.
* TheCameo: Anguirus and Rodan, during the Monster Island scenes.
* DolledUpInstallment: It wasn't going to be a Godzilla movie at first, but Toho had doubts about Jet Jaguar being able to carry the film by himself.
* DumbMuscle: Megalon. Seriously. Removing Jet Jaguar as a guide reduced him to basically nonfunctionality.
* FanServiceExtra: If the watcher can get over how strangely dressed they are the Seatopian dancing women are indeed mostly wearing swim suits and boots.
** The pin up girls on the back of the truck.
* GratuitousEnglish: In the last part of the film Rokuro is wearing a [[ComicStrip/{{Peanuts}} Snoopy]] sweatshirt with a "That was a stupid thing to do" thought balloon.
* ItIsPronouncedTropay: Jet Jaguar's name is always pronounced as the British "Jag-you-ar".
* MacGuffin: Jet Jaguar arguably serves as one for the first two-thirds of the plot, first guiding Megalon and then serving as the means to contact Godzilla.
* MinimalistCast: The number of characters with on-screen, speaking roles can be counted on two hands.
* OpeningMonologue: Ted Thomas' deadpan delivery of "In the first part of 1971, on a small island near the Aleutians..." in the English version is unforgettable and has become a bit of a meme to a few.
* PlotHole: A minor one: Our heroes suddenly know Megalon's name despite never being informed of it. Averted in the dub, in which Megalon is only referred to as "the monster" by the surface dwellers.
* PoorlyDisguisedPilot / StillBornFranchise: This was going to be a vehicle to cash in on ''Series/{{Ultraman}}''. Needless to say, it didn't work. Which makes Godzilla's [[CanonImmigrant appearance]] in ''Zone Fighter'' HilariousInHindsight.
* RecursiveTranslation: Robert Dunham, who played the Seatopian Leader, read his lines in English on set, was dubbed into Japanese (by Creator/GoroNaya), and then those lines were translated back into English. [[HongKongDub It shows]].
* RingOfFire: Megalon manages to trap Godzilla and Jet Jaguar in one until Jet Jaguar flies them out.
* RippedFromTheHeadlines: The United States did in fact conduct an underground nuclear test in 1971 on the Aleutian island of [[https://en.wikipedia.org/wiki/Amchitka Amchitka]], but, contrary to the opening narration, it was in November, not the "first part" of the year.
* ScrewThisImOuttaHere: At the climax of the ending fight, [[spoiler:Gigan flies off after taking a couple of shots of Godzilla's atomic breath, while Megalon, after getting double-teamed by Godzilla and Jet Jaguar, flees to one of Seatopia's underground doorways, which Seatopia detonates immediately after.]]
* ShootTheHostageTaker: When Gigan grabs Jet Jaguar and tries to use him as a shield, Godzilla blasts him in the face with his atomic breath without missing a beat.
* SizeShifter: Jet Jaguar, for no discernible reason!
* TheSongRemainsTheSame: Foreign dubs usually end with the untranslated version of "Godzilla and Jet Jaguar: Punch! Punch! Punch!"[[note]]the Italian dub just uses the instrumental bed[[/note]]. The song's [[http://godzilla.wikia.com/wiki/Godzilla_and_Jet_Jaguar:_Punch!_Punch!_Punch! Japanese lyrics]] are only ''slightly'' less goofy than the ''Series/MysteryScienceTheater3000'' GagSub.
* StockFootage: Oh yes.
** The footage of the "nuclear test" at the beginning is from the end of ''Film/EbirahHorrorOfTheDeep''. Godzilla jumping into the ocean is also from the same film.
** Megalon's powers seemed to be made for this. His lightning attack is an excuse to borrow King Ghidorah's Gravity Beam footage and his Napalm bombs are built for generic explosion scenes.
** The three tanks being blow torched make their fourth appearance since ''Film/MothraVsGodzilla''.
** One shot of the tanks has [[Film/GodzillaVsGigan King Ghidorah and Gigan approaching in the background]].
** Megalon's arms infamously turn into Gigan's hooks when he's destroying planes.
** The sequence of Gigan ducking for cover behind trees from ''Godzilla vs. Gigan'', which was already mostly made up of stock footage taken from ''Film/WarOfTheGargantuas'', is reenacted here by Megalon. Like in ''vs. Gigan'', it's plainly obvious that the creature moving behind the trees is a hairy Gargantua.
* TemptingFate: Rokuro tells Jinkawa he feels more secure driving vehicles on land instead of water. Cue him getting kidnapped by the Seatopians minutes later.
* VillainousFriendship: Megalon and Gigan seem to have shades of this in their interactions.