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when does the flash show up in supergirl
Worlds Finest, the eighteenth episode in the first season of the CBS television series Supergirl, features an appearance by The Flash
when does the flash reveal his identity in the eighteenth episode of supergirl
The speedster introduces himself as Barry Allen, a.k.a. the Flash, after Kara reveals herself as Supergirl in the 18th episode of season 1 of Supergirl
did cat know the flash's identity in the 18th episode of supergirl
In the 18th episode of Supergirl, Cat reveals to Kara that she knew Barry Allen was the Flash all along.

Question: who play barry
Self-contained rewrite: who plays barry allen in supergirl