The more I think about it, for all intents and purposes, Jor-El was a mad scientist. He espoused scientific theories well outside the accepted norm and performed numerous unauthorized scientific experiments of questionable ethics.
Superman #83 starts with Jor-El inventing a longevity serum. To test it, he proceeds straight to animal trials — well, animal trial, really. He only tests it on one animal. Now, he doesn’t start small and test it on a rat, monkey, or even a guinea pig — but instead he heads out to a nearby Kryptonian nature preserve and elects to test his serum on a Snagriff, a large dragon-like creature1. Almost immediately, he notices side effects — the Snagriff’s hide turns metallic and it starts eating all the metal in sight. The creature escapes Jor-El’s lab and runs rampant through the city. Finally, Jor-El captures it and maroons it on one of Krypton’s moons2 — but a metallic one, so at least it has something to eat.
When Krypton explodes, the Snagriff is hurtled into space, where — of course — it eventually lands on Earth3, 4. Immediately, the creature starts eating all the metal it can find. The police and army try to stop it, but they have no success. This is a Kryptonian creature on Earth after all, so it has all the standard Kryptonian powers including invulnerability and heat vision. Superman intervenes, but even he has a tough time battling the Snagriff. Things go from bad to worse when an alarmed scientist informs Superman that the monster has just eaten six nuclear bombs. Superman tries a different tactic now. He stretches his cape until it is large enough to contain the Snagriff5. He then ensnares the creature in his cape, and flies it up into outer space, where it explodes harmlessly, the nuclear explosion contained by Superman’s cape.
1. It’s not clear what Jor-El’s experimental plan was, or if he even had one. Was he just going to watch the Snagriff until it died – or didn’t die – of old age?
2. The KSPCA has a long file on Jor-El.
3. Why do all things Kryptonian end up on Earth?
4. At least this is proof the longevity serum worked – the Snagriff lived long enough to travel from Krypton to Earth. And the serum apparently protected him from the rigors of travel through space as well.
5. No, I have no idea how he was able to stretch out his cape so large, and then unstretch it later.