This movie falls into the category of so bad it's not good, but it is unintentionally funny.

When nuclear testing causes disturbances across the area, including the underwater world of Seatopia, their leader, Emperor Antonio, clad in a white toga with go-go boots and wearing a tiara with what looks like a replica of Megalon's head, calls for the giant cockroach to appear and retaliate against the humans. Megalon heads to Tokyo and starts tearing things up in town.

Meanwhile back at a Japanese lab a couple of humans and a kid are admiring the new robot they've created, Jet Jaguar, which was likely brought in to make the movie even more kid friendly. It reminded me of a creepy clown Ultraman. A couple of Seatopians show up and the kidnappings begin because they want the robot technology.

Ultimately, Jet Jaguar and Godzilla team up against Megalon and Gigan. It takes until two thirds of the movie to get the monster action going but when they do the fun begins. There are monster high fives and handshakes, dispelling any notion that these are giants guided by instinct.

When Godzilla shows up, the music doesn't announce a scary monster, it sounds more like someone's drunk Uncle Tony is stumbling onto the scene. The music was not very inspiring in this movie.

A giant cockroach seems apropos as a mortal enemy, they were here long before humans and will likely be here long after humans. I've always thought they'll be the ones to take over once we're gone in the hopefully very distant future. Thankfully, this time a giant irradiated lizard was able to keep cockroach world domination at bay.