Issue: Journey into Mystery # 90
Writer: Stan Lee / Larry Lieber
Artist: Al Hartley
Publication Date: March 1963
Dr. Don Blake decides to reveal his identity as Thor to Nurse Jane, but before he can do so he receives a message from Odin telling him that this is a big no-no. Shortly after this, Blake notices that everyone in the city has gone a little nuts, doing strange things. He turns into Thor and pays a visit to Mayor Harris, but the mayor wants Thor arrested. Madness! Thor thinks back to counseling from Odin, and believes that the people of the city are actually impostors. Thor finds a spaceship, but when he approaches it a magnetic force holds him to the hull, and he loses his grip on his hammer. Turns out its the Xartans from planet Xarta, who can impersonate anyone. They, um...are quite different from these guys. They are planning on taking over earth, obviously. Blake says if the Xartans free him he can lead them to Thor, the only one who might stop them. However, doing this makes him look like a coward in front of Nurse Jane and Mayor Harris, who are being held captive by the Xartans. Blake then is able to go retrieve his hammer and become Thor. Thor fights the Xartans, who can change their shape, and defeats their champion, thus causing the rest of the Xartans to flee. Of the remaining Xartans on earth Thor demands they turn into trees, and in doing this, the Xartans lose their ability to think, for they fully take on the characteristics of anything they morph into. Thor: 1, Xartans: 0, Skrulls: 0, Trees & Cows: Draw, Mole Man: 0.
Writing just about every Marvel superhero comic under the sun seems to be taking its toll on Stan a little, as he's really recycling with this story. There's not much at all that distinguishes the Xartans from the Skrulls, other than their skin color. This of course makes me wonder why its the Skrulls that became super popular and have returned time and again to try to conquer earth, and why the Xartans just turned into a bunch of trees and seemingly disappeared forever. I'll keep my eye out for these aliens, but they certainly never gained the popularity of the Skrulls. Maybe in a few months Spider-Man will turn a bunch of wookies into toasters.
No, that's not Invisible Girl gut punching the god of Thunder, although I can see where you'd be confused. It's one of the Xartans who turned invisible. Once you know what you're looking for, it's easy to tell the difference.
Next: Strange Tales # 106