I started Supergirl last week and am sort of already obsessed. Apparently, the DC series do a decent amount of crossovers, so for example, in Supergirl The Flash accidentally traveled to Supergirl's Earth (Earth-38) and ended up helping her fight bad guys before returning. There were cute moments of them bonding over being superheroes and hanging out together which adds to the heart within the show, plus it wasn't in a romantic way either but just platonically and it showed the side of superheroes that you want to see — them just being dorky and acting like real people. Anyways, if anyone's looking for some new shows I would recommend checking them out.