An adult version of Superman (Kal-El) has appeared on Supergirl as a blurry, shadowy and backlit figure, but in next month's “For The Girl Who Has Everything” episode a teenaged version of the Last Son of Krypton will come into focus.
In the episode, Kara (Melissa Benoist) wakes up in a dream world where her home planet was never destroyed. Since Krypton is alive and well, that means Kal-El never had to be sent to Earth, so we'll get to meet a 13-year-old version of Kara's cousin.
Daniel DiMaggio (Tales of Halloween, Burn Notice) will play the future-Superman. Because his appearance comes in the form of a dream, it seem reasonable to believe it would be a one-off, however, the casting call listed it as "potentially recurring." So, we might see DiMaggio's Kal-El in Smallville flashbacks or as a holographic character, like Kara's mother.
“For The Girl Who Has Everything” episode of Supergirl airs Monday, Feb. 8 at 8PM on CBS.