Warning: Do not read if you haven’t watched Monday’s episode of The CW’s five-part crossover, “Crisis on Infinite Earths.” Major spoilers ahead.

It was a “Smallville” reunion for the ages.

Tom Welling and Erica Durance reunited for the first time in more than eight years as Clark Kent and Lois Lane in Part 2 of The CW’s five-part DC crossover event, “Crisis on Infinite Earths,” which aired on Monday’s “Batwoman”. It’s the first significant appearance made by the TV couple since the WB/CW superhero series, “Smallville”, left the air in 2011.

Welling and Durance’s Clark and Lois — living a content and happy life as a married couple with two young daughters on Earth-167, long retired from superhero life — came face to face with another Clark and Lois (Tyler Hoechlin and Bitsie Tulloch), when they dropped onto a very familiar-looking farm in Smallville, Kansas, via a universe-jumping time device, along with Iris West-Allen (“The Flash”‘s Candice Patton), desperately seeking their help amid a worlds-ending crisis.

“We had conversations about how to best see Tom again and we knew that we really wanted Brandon Routh as Clark Kent in the Daily Planet. I think the Tom Welling/Clark Kent that we all picture when we think of him is Clark on the farm. So it made sense that the farm is still there,” “Batwoman” executive producer Caroline Dries told reporters recently following a “Crisis on Infinite Earths” screening.

“Tom was joking when he was there [on set], ‘Oh, that cow recognized me,'” Dries added, prompting some laughs. “It all felt very 10 years ago in a great way. To us, it just felt natural that that’s his natural environment where we’d see him.”

The episode also features “Legends of Tomorrow”‘s Routh reprising his titular “Superman Returns” role (and going dark!), as well as Jon Cryer returning as Lex Luthor, though Welling’s Clark, of course, doesn’t recognize him. His Lex, he says, is president of the United States, an Easter egg from “Smallville”. (Michael Rosenbaum played Lex on “Smallville”.) With Welling, Hoechlin and Routh representing the red and blue on “Crisis,” did the writers ever write a scene where the three Clark Kents interacted?

“We never wrote that, but like Caroline was saying, in terms of putting Brandon and Tom in a scene together, they were working across purposes because we wanted Brandon at the Daily Planet and we wanted Tom on the farm,” said Arrow-verse executive producer Marc Guggenheim, pointing instead to the recently announced “Crisis” comic book from DC Comics. “But… the desire to have multiple Supermen is what inspired the backup story in the ‘Crisis’ two-parter [in the new comics, announced Thursday]. It’s every Lex Luthor you can imagine and every Superman you can imagine. So at least we’re doing that.”

Tulloch also shared insight into what it was like being in the same scene with another Lois Lane in Durance. “Yeah, I worked with Erica in some capacity… She’s lovely,” the actress told ET. “I wouldn’t say anyone was really comparing notes just because there were a couple of Supermen too and I think everybody really respects that people are bringing their own individuality and their own interpretation of these characters.”

But “Smallville” fans very well will have noticed that Welling’s Clark is without powers on Earth-167, a decision that was made by the writers early on in the process — and was given Welling’s approval. (The final shot in the “Smallville” series finale, to compare, featured Welling’s Clark fully embracing his destiny as Superman, revealing the iconic suit as he flies off to fight crime.) “It felt incredibly necessary in the moment,” Dries explained, the way of which is a question meant to intrigue.

The producers had been eyeing Welling for a meaty “Crisis on Infinite Earths” cameo for a while and approached him with the “Smallville” scene already written. According to Dries, the 42-year-old actor “was cool with” where the character eventually ended up.

“He was terrific. We got on the phone with him and basically pitched him everything. The scene that [“Batwoman” writers] Don [Whitehead] and Holly [Henderson] wrote was already done and we just emailed it to him. And he was like, ‘I love this,'” Guggenheim recalled. “He basically said to me, ‘You guys have basically written the one scene that I can’t say no to,’ which was really, really nice.”

“When you talk about the interactions… that’s my favourite scene,” he continued. “I feel like every note — even Tom’s little facial expressions when he says, ‘Oh, still stronger,’ [after he punches Cryer’s Lex Luthor] is great.”

“Crisis on Infinite Earths” continues on “The Flash” on Tuesday, Dec. 10 at 8 p.m. ET/PT on The CW.

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