“The Five Legion Orphans” was only 12 pages long. To fill the rest of the book, one would expect that perhaps a new Superboy adventure would have been commissioned. Perhaps another outing by Otto Binder, who had given us “The Six-Legged Legionnaire” last issue. What we got, instead, was the closest Silver Age readers were going to get to an explanation of why Star Boy first appeared with powers identical to Superboy, and, when he showed up again after missing 19 Legion adventures, was suddenly equipped only to make things super heavy.
The explanation comes in a text box added to the last panel of 356’s reprint of “Lana Lang and the Legion of Super-Heroes,” a story written by the aforementioned Otto Binder.
A note on the Grand Comics Database entry for this reprint says that Star Boy was “partially refried from Adventure #195.” Partially refried? Like the beans?
Turns out Adventure #195 contains a story titled “Lana Lang’s Romance on Mars,” which matches “Lana Lang and the Legion of Super-Heroes” pretty much page-for-page. Both open with Lana’s collection of photos of her dream boy’s adventures, with Clark using his powers to light Pa Kent’s cigar, and with Lana going to the movies and getting the idea to make Superboy jealous so he’ll pay more attention to her. Then Superboy receives a message to meet an unknown troublemaker at a spot that sounds like its name was lifted from The Adventures of Tom Sawyer, and goes to find another super-powered, teenaged boy from another world.
Only in the pre-Silver Age Adventure, the other boy is named Marsboy, not Star Boy. Just like Star Boy in the later story, he has come to Earth to catch a criminal from his home planet, whom he has imprisoned in a cave. Just like Star Boy, Marsboy has X-Ray vision that can see through lead but not copper, and, just like Star Boy, he has come to ask for Superboy’s help catching a second criminal on his home planet, one who has hidden in a copper-lined labyrinth.
Lana Lang overhears the exchange between both boys and Superboy, and, having learned the boys’ secret identities, blackmails them both into pretending to be her boyfriend so that Superboy will be jealous. Both boys take Lana to their respective planets and shower her with gifts. In both cases, Superboy hooks up with another girl—Cytherea on Mars and Zynthia on Xanthu—and thus forces Lana to admit her mischievous plan. (Note that, in the pre-Star Boy adventure, Lana calls her rival “Dream Girl.” Heh.) 
Yep, Star Boy began life as a simple re-tread of another character.
The first of the two stories has no credited writer, and falls between stories written by Jerry Coleman and William Woolfolk, so it’s hard to speculate. Otto Binder’s first credited story for DC Comics was in Action Comics #186, in November, 1953. That was a Tommy Tomorrow adventure. His first credited Superboy story came in June of the next year, and appears to be his first DC super-hero story. Credited. Perhaps he did write the original Lana Lang / Marsboy piece? Hard to say. Legally, of course, DC owned both stories and had every right to re-use them in any fashion they saw fit.
The only differences here are that Zynthia is actually Star Boy’s girlfriend, while Cytherea is just a good Samaritan willing to help an Earthboy in need; Star Boy is a Legion Member from the 30th Century, and Marsboy is an old friend of Superboy.
Wait… what?
Who is this Marsboy kid, and when did he and Superboy become “super-friends?” Turns out that Marsboy first appeared in very early issues of Superboy’s own title, debuting in #14. He was co-created by the legendary Curt Swan, who also drew the Marsboy appearance in Adventure #195. Sadly, it’s unknown which writer chronicled his adventures. (Star Boy was co-created by Otto Binder in an adventure re-drawn by Superboy’s regular penciller, George Papp.)
Marsboy came to Earth to steal the Sphinx from Egypt, because it contained the secret of creating additional water on Mars. Mars, it seems, was an Earth colony, originally settled by denizens of the lost civilization of Mu. Like Ultra Boy after him, Marsboy adopted a secret identity on Earth (“Joe Mars”) and enrolled in school with Clark Kent.
In their super-identities, the boys were, um, rivals…
Though they occasionally got undressed in outer space together, as you do.
In day-to-day life, they behaved like, well, special friends.
Of course, despite Marsboy’s original orders to destroy Superboy, the two realized that Marsboy didn’t need the whole sphinx, he just needed a secret formula hidden inside it. Superboy’s X-Ray vision could read the formula through its copper covering, where Marsboy’s couldn’t. Mars was saved. The sphinx was saved—although being flung like a javelin into the upper atmosphere probably didn’t do it much good, structurally. And love—er—friendship—conquered all. (Seriously, though, there’s more tension between these two than there ever was between Clark and Lana. I mean, what’s she thinking below?)
Not cool, Lana. The guy has a boyfriend. Jeez.
So, clearly, editorial decided to do a quick-and-dirty makeover of an old story in order to cash in on the growing popularity of the Legion, and Star Boy was born. But what’s the in-continuity explanation (for those of us who care about such things) for the same set of events happening twice to Superboy and Lana, with two different heroes in the third slot? It would be really cool to say that, all of Marsboy’s appearances happening as they do before Barry Allen first appeared in Showcase #4, and before J’onn J’onzz came to Earth in the pages of Detective Comics, he’s an Earth Two hero. But the adventures of Superboy in the Golden Age are accepted as the teen adventures of the Earth One Superman. Kal-L of Earth Two was never Superboy.
Marsboy, then, must come from some other numbered or lettered Earth in the Multiverse, where there was a Superboy in 1950. But wouldn’t Marsboy and the Legion of Earth Two have been a cool title?