It was The Flash, but with Arrow and Supergirl characters.
Flash on a Sunday? o.0
They rearranged the schedule this week. Probably because even the crossover episodes tend to focus on their own show's characters a little more and there are some uh...things that would be better for Supergirl to get the focus later on.
This episode actually had a metajoke with Ralph about the latest crisis: "It's not even a Tuesday."