The X from Outer Space

The spaceship AAB Gamma is dispatched from Japan to the planet Mars to investigate reports of UFOs seen near the Red Planet. When the spaceship arrives, it comes across a mysterious alien vessel that suddenly sprays the AAB Gamma with spores. Samples are returned to Earth, where one of them begins to develop.

The spore grows into a giant, lizard-like creature that is named "Guilala". The monster begins a reign of destruction through Tokyo. It spits fireballs, feeds on nuclear fuel, turns into a flying, burning sphere, and destroys all aircraft and tanks in its path. Guilala is finally defeated by fighter jets laden with bombs, which coat it in a substance called "Guilalalium". This causes Guilala to shrink down to its original spore form. The government promptly launches it back into space, where it will circle the Sun in an endless orbit.