along with Captain Marvel, Batman, and Superman. Not exact depictions of those characters, but recognizable nonetheless.
In "Master Race" by Richard Ashby, a scout for an alien invasion of the Earth lands near a boy's treehouse and brings back a few of his belongings for the perusal of his superiors. After seeing Earth's comic books they hastily flee the solar system, believing that Earth has superheroes who could smash any invasion, just like in the comics. Batman in referred to by name ( as "Bat Man" ), as is Buck Rogers and Mandrake the Magician. Captain Marvel was still being published at the time, but would be cancelled within a couple of years because of a plagerism lawsuit filed by DC comics, publisher of Superman.