>>11543972
>And the people GI Joe fights call themselves Cobra and sometimes have visible snake theming. Basically you'd have Skeletor and the Snake Men open a portal to Earth and meet them, requiring any Heroic Warriors in the crossover to go find the US military (it makes the most sense if they include Marlena, so they won't).

Yeah you're on the same track I was. Have Skelly and the Snake Men reverse engineer the cosmic key. Skeletor dethrones Hiss and takes his power (leading to the release of Concept Hiss) only to return with Cobra weaponry to Eternia, while aiding in an invasion of Earth alongside Cobra commander. Then the heroes find out independently of each other and establish contact before going into all out war. The Joes would get Eternian upgrades, and the Heroic Warriors would all get tacticool militaristic ones. Maybe all the bad guys end up with a thulsa doom look?