I imagine that as has been shown that Batman exists in the Kara universe, so I imagine he and Clark are friends. Clark, would then be the link that would unite Kara to the bat-world. From this assumption, I imagine that Barbara, following a hint from Batman, could do an internship with the DEO IT staff. As villains of the episode, obviously we would have the Gothan Sirens, Catwoman, Poison Ivy and Harley Queen. Will be great!!!!