Few actors can claim that they’ve appeared in multiple iterations of a fan-favorite franchise, but John Wesley Shipp and Mark Hamill are two such men. Shipp played Barry Allen in CBS’ 1990 version of “The Flash,” and now plays Barry’s (Grant Gustin) father, Henry Allen, in The CW’s successful reboot. This week, Shipp is filming alongside “Star Wars” veteran (and fellow ’90s “Flash” alum) Mark Hamill, who is reprising his original role as the Scarlet Speedster’s nemesis, James Jesse, aka The Trickster. (Spoilers ahead.)

We won’t see Hamill on screen until the 17th episode of “Flash’s” freshman season, but Variety spoke to Shipp about reuniting with his former costar and what’s ahead for Henry now that his son has come face to face with the man responsible for murdering Barry’s mother, the Reverse Flash — who, unbeknownst to Barry, is actually his STAR Labs mentor, Harrison Wells (Tom Cavanagh). Although Henry is still falsely imprisoned for the crime, Joe West (Jesse L. Martin), Barry’s guardian, now believes in Henry’s innocence, which will lead the duo to join forces in this week’s episode, “Crazy for You.”

It seems like Henry’s been keeping a low profile in Iron Heights thus far, but in this week’s episode, he gets a beatdown after trying to help Barry and Joe; how does that affect him going forward, beyond the immediate physical implications?

The fun thing about this episode is that now that I know that Joe [believes me] … that was a bit of a testy moment, when Joe admitted that he knew that I did not kill my wife. Since then, for Henry it’s been like, “Now they know that I’m innocent, how do I get involved?” I’m stuck behind that glass and all of my interactions are behind that glass. The fun thing about this episode is, over Barry’s objections, I start — with Joe — asking questions around the prison and I sort of get my head handed to me. That lands me in the infirmary. What that allows Barry and Henry is to have some face-to-face time not through a partition. So, suddenly we see his father and him together in a more intimate setting where they’re not separated… and that’s fun to play.

Was that liberating for you to play, after Henry has spent so long confined?

What’s been amazing to me so far is we’ve had four father/son heart to hearts through the glass. After about the second one, certainly after the third one I was thinking, “we’ve done it. There’s no other way that they can write the heart to heart, father/son moments,” but they keep surprising me. Even given the additional benefit of not being through the glass, there’s another heart to heart. I read the script and I said “I’ll be…” It’s just amazing. They have found one more interesting way to come at this. I’ve been very gratified because the fans talk about the “major feels” whenever there’s a scene — also between Joe and Barry – but between Henry and Barry.

One of the reasons is that they don’t write the same scene every time. They always find a new spin. Either Henry’s defeated and Barry’s trying to pump him up or Barry comes in after The Man in the Yellow Suit, defeated, and Henry’s telling him to be strong. Now in this episode there’s yet another way. It addresses and goes to the issue, does Henry recognize his son? The Flash comes in and saves him when he’s getting roughed up. Would a father recognize his son, and if he does, would he let the son know that he recognizes him or would he wait for the son to tell him? How does he open that window? That’s the brilliance of the writing in [this] episode for me as far as I’m concerned. Of course, many more fun things happen, but speaking selfishly…

What kind of dramatic impetus does it serve for Barry, seeing his father vulnerable? Henry’s been fairly insulated against the increasing insanity of Central City by being behind bars up until now.

I think what’s very interesting now is we could switch. It’s like Henry is almost caught with his hand in the candy jar. If anything, I think to a degree it pisses [Barry] off that this is another element. Now his father isn’t totally dependent on him from the inside; he now has other allies. How does that affect the father/son relationship because up until then the son has been the only one who has believed that Henry is innocent. So, as that begins to fan out, he’s no longer the only one who believes and the father is making more connections. How does that affect the son? I think that’s another interesting dynamic. I’ll tell you, these writers don’t miss a trick. That’s what I’ve been so delighted about. You know, it’s not just an adventure, fun ride at the amusement park. They are getting the relationships and the layers right.

When we were at the CW Upfronts, I had not seen our first pilot scene and Grant came up to me and he said, “Oh my God, our scene is so wonderful.” I had to sit there and say, “Okay, it’s not cool to cry during your own scene.” I said, “I’m glad to hear that,” because if it had turned out not to be moving that would have been our fault, Grant’s and my fault, because it’s written, it’s set up — they say if it ain’t on the page it ain’t on the stage. Well, it certainly is on the page.

Grant recently told me that Barry’s going to start being a little more honest with his father in the near future — how do you think that might alter their relationship?

I will be as excited to find out how that impacts our relationship as hopefully you are. I think one thing [Grant] does do that I see very clearly — and I think this is one thing that’s fascinating in Grant’s portrayal — is that his scenes with Henry are differentiated from his scenes with Joe because he comes to Henry almost as a little boy. That makes sense, because Henry raised him from birth to the age of 10. Joe essentially raised him from 10 into young adulthood. Even though we have similar scenes, if you notice the way Grant plays them, it’s qualitatively very different. That’s a smart actor right there.

Speaking of those different dynamics; one of my favorite aspects of the show is that Barry has three important male role models in his life with Henry, Joe and Wells, and each relationship is different. Is there any part of Henry that feels threatened or a little replaced by Barry’s connection to Joe or Wells?

Absolutely. You know, we went through a couple of drafts of the scene where Joe comes in to tell Henry [he believes him]. The first pass at it, I don’t think any of us felt was right because Henry was too much the saint. He was too forgiving. He let Joe off the hook and I said, “Wait a minute, I’ve been in prison for 14 years, in the hell on earth that is Iron Heights. Another man has raised my son and to add insult to injury, turned him into a policeman like him instead of a heart surgeon like me and I’m going to go ‘that’s okay?’” So that’s where we got the bit of a testy [scene] where he says “I should’ve come before now” and Henry says, “You just weren’t up for a little chitchat with the man who murdered his wife in front of his own son?”

So what Andrew came up with, which was so lovely, was, “don’t let him off the hook. But recognize what would have happened to Barry if Joe hadn’t stepped up.” I get two things to play in that scene — actors love that. By holding on to my anger that my friend has been convinced — and trying to convince my son for 14 years — that I’m guilty, on the other hand, I have to be grateful that he stepped in and stepped up and took Barry in. I love that scene with Joe for that reason.

Mark Hamill is on set this week — how has it been to reunite with him?

It’s been great… Mark said a very interesting thing to me. We shared a ride back to the hotel one night. He said, talking about himself, “This is the second time in a row” — talking about “Star Wars” — “that I’ve gotten to revisit a project that I thought I would never see again. We are really in a very unique and fortunate position, aren’t we?” I said, “Yes. I thought that. I never thought I’d see ‘The Flash’ again, 24 years later.” I get a role that’s not a walkthrough but that is intimately involved in the story. It really is something.

Beyond that, I just want to say the relationship, the structure of the relationship between Mark, the old Trickster and the new Trickster [Devon Graye] is fascinating. Talk about layers. How do they bring Mark back 24 years later in a role that he played 24 years ago playing the same character? Obviously, they can’t write it the same way, so they get the best of both possible worlds. They get the youth and the wannabe and they get Mark’s history and gravitas and everything that he brings to the role as well.

What’s the dynamic between James Jesse and Henry in Iron Heights?

The only thing that’s different — well, obviously I’m playing different character — but Mark’s Trickster is now very much more seasoned. He too has been in Iron Heights, you know what I mean? So what we see out of Mark is a much more seasoned insanity. It’s quite chilling, actually, and that craziness is passed on to the next generation — to Devon. It’s more fun and games.

I was a big fan of Mark’s work as the Joker in the DC Animated Universe, so it’s great to see him revisiting that unhinged type of character — he plays the villain so well.

He really does. The secret to that is he’s a huge comic book fan. And people keep asking me, do I have anything from the suit or from the old series? I do. There is an Easter egg in this episode in the STAR Labs scene. Pay attention to what I’m wearing when I get to STAR Labs. I think some people will recognize it right away.

Your version of “The Flash” was obviously ahead of its time, given the current influx of superhero properties on TV and in film. I was curious about your take on the explosion of the genre, given you were kind of a precursor to everything that’s happening now.

You hit on it. We were right at the dawn of a genre exploding into the mass popular culture. I always define it this way: When we went to San Diego Comic-Con 24 years ago, I walked through in three hours, signed half a dozen autographs and that was it. This year, 180 thousand people had taken over the town. We premiered our pilot in front of seven thousand people. Comic books have gone mainstream. The audience is there. We are now stepping into it.

“The Flash” airs Tuesdays at 8 p.m. on The CW.