We learned a few weeks back that both Calista Flockhart and Tyler Hoechlin would be returning at the end of the second season of Supergirl. With Daxamite invasion happening, it's obvious to see why Supergirl (Melissa Benoist) can use Superman's help, but both Kal-El and Cat Grant play pivotal roles in the final two episodes. Executive producer Andrew Kreisberg told EW.com:
I don't want to tease too much about how they return because both Superman's return and Cat's return are great surprises; how it happens, you'll be shocked at both of their appearances. This is Kara's darkest hour. It's perfect that she has both Superman and Cat, who are these great stabilizing influences in her life — Cat, who tends to have a good handle on what Kara needs, and Clark has a pretty good handle on what Supergirl needs. She needs them both desperately because she's faced with some truly awful decisions to make in the finale and choices that affect her both as Kara and as Supergirl. Having her surrogate mother and surrogate brother there to make these decisions, it's good to have them there.
There are two episodes of Supergirl season two left and it airs Mondays at 8 PM on the CW.