'Barry's in Trouble' in "The Flash" Season 3 Premiere, Teases Reverse Flash, Matt Letscher

In "The Flash" Season 2 finale, Barry (Grant Gustin) made a decision that changed his entire world -- literally! He went back in time and prevented Reverse Flash from murdering his mother, which completely reset the timeline and rocketed Barry into a present that had changed dramatically. But what happened to Reverse Flash, now that he failed to accomplish what he set out to do?

Well, according to "The Flash" Season 3 sizzle reel, he's all locked up. Matt Letscher -- who plays the vengeful speedster from the future -- spoke with CBR about Reverse Flash's captivity, as well his excitement to be part of "Legends of Tomorrow's" Legion of Doom.

CBR News: Let's start out with something easy: What was your reaction when you received an invitation to join the Legion of Doom?

Matt Letscher: Utter glee. As an actor, it's a group of people I've really enjoyed working with in a limited fashion for the past couple of seasons, and I have a long history with some of them: Greg [Berlanti] and Marc [Guggenheim] and Andrew [Kriesberg] and Victor [Garber] in particular. It just fell in my lap, and I'm really looking forward to it.

Since Reverse Flash will be a series regular on "Legends of Tomorrow," is there any chance we're going to learn anything more about the future he comes from?

The moment you learn about it is probably the moment I'm going to learn about it, because I am given -- as an actor -- information on a need-to-know basis. They're very protective of it, and they also don't want to disappoint fans by saying, "This is how things are going to go," and then change mid-stream. They don't want to feed people expectations! But that's not what you really call it. I don't know what I just said.

I realize filming has just started on these shows, but have you had the opportunity to interact with the "Legends" cast yet?

Yes, I have. I've been up in Vancouver for a couple of weeks now, and we had a gathering or two and they started shooting. They were super welcoming and lovely and there's a bunch of change afoot for the show, which everybody seems really excited about. I think everybody feels really invigorated.

What was the atmosphere like on set, as opposed to that of "The Flash?"

There is definitely a different vibe. I love being on "The Flash." They're very warm. So far, what I've experienced about "Legends" is kind of a more raucous group, and that could be the fact that there may be a more diverse set of actors, but I don't know! We'll see when I spend more time with them. So far, really great.

In the "Flashpoint" comic, Reverse Flash was just jubilant that Barry gave in and changed the timeline. Does he have a similar mindset going into "Flash" Season 3?

It's more complicated than that in the premiere, but it's safe to say anything that causes Barry pain, the Reverse Flash is completely behind. You know, Barry messing with the timeline -- as all tried and true science fiction can tell -- is never a good thing. Anything causing problems for Barry, he's on board with.

By the time of the "The Flash" Season 3 premiere, Barry and Thawne have been in that alternate timeline together for a few months. How have they been getting on?

You may have noticed in the sizzle that I'm in a cage! That's an impediment in our relationship. It's not making us any closer. I don't think the Flash and Reverse Flash will ever see eye-to-eye on anything. I think that's something we'll continue to see as the show goes on.

Alright, so to sum up, Barry and Thawne aren't quite seeing eye-to-eye -- but what about you and Grant Gustin?

Oh, I love Grant! Grant has a huge workload on his shoulders with this show. It is a tremendously labor-intensive show for him, and he handles it with incredible grace and professionalism and I think he's really talented. I just so enjoyed the stuff I had to do with him in the season premiere. I just can't say enough good things about the guy. I think he's super talented.

In my opinion, you had the two best lines in the "Flash" Season 3 teaser, one of which was a "Flashpoint" namedrop. What was it like to get to deliver the one word fans have been dying to hear since Season 1?

It was a classic kind of Andrew Kriesberg flourish, which I love. It was really enjoyable. Knowing that that's something that's really going to play with the fans, and being gifted something like that, is kind of delicious, like being given dessert before dinner. I just had a great time with it, and the fan response has been really amazing when it comes to that... it's fun. It's fun to be part of a moment like that.

Could you sum up "The Flash" season premiere in three words?

In three words, can I sum up "The Flash" season premiere... I'm not great at this, but I would say, "Barry's in trouble." Barry's in trouble!

Now that you've appeared on two DCTV shows set in the "Arrow"-verse, do you hope to make it onto "Arrow" or maybe even "Supergirl?"

Absolutely! I want to complete the foursome. I want the whole set on my resume! I would love for that to happen. You know, there's a lot of crossover happening this year, so there's a decent chance I've got a shot at it. We'll see!

Starring Grant Gustin, Jesse L. Martin, Carlos Valdes and more, "The Flash" returns to The CW on October 4 at 8 pm EST. Starring Brandon Routh, Caity Lotz, Arthur Darville and more, "Legends of Tomorrow" returns to The CW for its second season on Thursday, Oct. 13, at 8 p.m. ET/PT.

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