Krypton, the new SyFy series that tells the story of the House of El — you know, the reason Superman and Supergirl have to explain that it's not an "S" on their capes — takes place before the fated baby is placed in a pod and sent to planet Earth. That said, will Superman be on Krypton? Based on what goes down in this story, it doesn't seem quite as out of question as you might think.
For one thing, Krypton is not part of an established DC comics shared universe as far as superhero or comic book series go. Like Gotham, or The Gifted for Marvel fans, this is a stand-alone series. So if Superman were to show up, they'd have to bring in someone other than the CW's Tyler Hoechlin or the DC Extended Universe's Henry Cavill, mustache optional. That's a tall casting order — how many Clarks can we as a culture handle at once? But comics confusion is fairly common between franchises. According to The Hollywood Reporter, the DC comics character Hawkwoman will appear on Krypton, and the similar character Hawkgirl is part of the Arrow-verse. Plus, you may recognize actor Ann Ogbomo who plays Jayna-Zod on Krypton, because she's a freakin' Amazon in Wonder Woman and Justice League.
On the other hand, Krypton isn't a straight prequel. While it appears to be primarily set in the comic book past, the present/future creeps in and Superman does play a part in the plot, it seems. In the trailers and promos for the series, Kal-El's grandfather Seg is made aware that his family includes the greatest hero that the galaxy will ever know. Seg is even given one of those legendary capes. If he's working to save Krypton in the name of his grandson's future legacy, then there is room in the story for Kal-El to show up in some form. Even if it's just a flashback, or maybe more like a flash forward or sideways situation, it's possible.
Then again, the same way Supergirl only utilizes the last son of Krypton when they absolutely need to in order not to draw focus from Kara, this is Seg's story. The future gramps has a lot to accomplish in his own life, first and foremost restoring the House of El's name so that they can even start a legacy. So if Superman were to appear, he probably wouldn't stay long. There's also something poetic and sad about the fact that Kal-El never really got to experience Krypton. Him showing up in the city of Kandor takes away from one of his only weaknesses, and honestly he might not even like the struggling society that he finds there.
“This is not a superhero show,” actor Cameron Cuffe, who plays Seg, said in an interview with Variety. “No one is fighting crime or slapping on a mask. No one is fighting for truth, justice and the Kandorian way." In the same interview, creator Cameron Welsh insisted, “What you thought you knew about Krypton, you can forget."
If you comb through interviews with the creators, it does not appear that the creators have outright said whether we can expect to see Superman, or some version of Kal-El, on Krypton. Maybe that means that there is truly no chance it'll happen... or maybe it means that that question was off the table, and preemptive "pleading the fifth" is a clue in and of itself. In an interview with Bustle, however, actor Georgina Campbell, who plays Lyta, says, "Even if you're not a fan of Superman you can still relate to it and enjoy it because, you know, Superman's not in it!" Whether that changes in future seasons remains to be seen.
So, don't get your hopes up that Krypton will eventually showcase Superman in this prequel. A young Jor-El (Superman's father) might be more likely, and the creators have teased many more (and surprising) DC characters to come as the season progresses. That guessing game should be plenty for fans. For now, this is a story about Seg-El, Lyta-Zod, and the Kryptonians just trying to survive and not realizing exactly what the future holds.