Supergirl wraps up the annual crossover with “Elseworlds, Part 3.” Picking up pretty much where the last part left off, Barry and Oliver, now being seen as the outlaw Trigger Twins, face off against a black-suited Superman, who proves to be Dr. Deegan, the man causing all the problems for our heroes. The introductory voice over is even done by Deegan, although the phrasing sounds like it’s borrowed from Arrow’s usual lead in.