Fantastic Four (1961) 2-B

"The Fantastic Four Meet the Skrulls From Outer Space!"
The members of the Fantastic Four are apparently committing crimes in broad daylight. Theft, sabatoge, vandalism. It all becomes clear when we see that the crimes have been committed by Skrulls, shape-shifting aliens who know that the only way to successfully invade Earth is to eliminate the Fantastic Four.

"Part 2: Prisoner of the Skrulls"
The army captures and imprisons the FF for their crimes. No jails can hold them for long, however. Johnny infiltrates the Skrull band and, once he is at their base, fires the flare summoning the team.

"The Fantastic Four Fight Back!"
The Invisible Girl, Thing, and Torch battle the Skrulls while Mr. Fantastic travels to the Skrull command ship, posing as a Skrull, reports that Earth is impossible to conquer.

"The Fantastic Four...Captured!"
Upon their return, the FF must convince the army of exactly what happened. They hypnotize the three captive Skrulls into becoming cows and forgetting who they really are.

First appearance of Skrulls.