With The CW's new spin-off series The Flash in production, new cast members keep coming on board, such as last week's addition of Robbie Amell as Ronnie Raymond, a.k.a. Firestorm. Over the weekend, William Sadler revealed on his Twitter page that he has joined the cast as Simon Stagg, sending out a number of photos from the set. Take a look at these photos, then read on for more information.

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In the DC Comic books, Simon Stagg was the CEO of Stagg Enterprises, who has connections to adventurer Rex Mason, a.k.a. Metamorpho. Since Katana (Devon Aoki) has already been confirmed to star in Season 3 of CW's Arrow, its possible that the network could be setting up a crossover that features The Outsiders, a superhero group that includes Metamorpho, Katana, Black Lightning, Owl-Man, Creeper, Geo-Force, The Eradicator, Halo and Olympian II.

It isn't known if William Sadler is only guest starring in one episode of The Flash, or if he has a multi-episode arc. It's possible that we'll learn more about his involvement when during the show's Comic-Con 2014 panel, so stay tuned for more information.