Smallville fans have been jumping for joy following news that Tom Welling would be reprising his role as Clark Kent/Superman, alongside Erica Durance as Lois Lane, for the Arrowverse's TV crossover event "Crisis on Infinite Earths." However, one face that won't be returning from the beloved CW series is Michael Rosenbaum, aka Lex Luthor, and now we know why.

Rosenbaum, who impressed fans as the bald-headed genius in the series that ran from 2001-2011, revealed via Twitter he wasn't given sufficient details by the network on the plot, as well as any indication that he'd actually be paid, leading to him turning down the role.

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"Friends, many of you have tweeted and asked me about joining the Infinite Crossover," Rosenbaum tweeted. "I can't tell you how much this means to me. I'll just be straight up about this. WB called my agents Friday afternoon when I was in Florida visiting my grandfather in a nursing home. Their offer: No Script. No idea what I'm doing. No idea when I'm shooting. Basically no money."

"And the real kick in the ass 'We have to know now.' My simple answer was 'Pass'. I think you can understand why. I hope this answers all of your questions. Lovingly Rosenbaum," he concluded.

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This will surely disappoint fans, as The CW made it clear Welling's return was a priority and fans assumed this would be the same for the supporting cast. Rosenbaum did admit in the past he and Welling didn't speak about the crossover or a reunion, and while some thought he was just playing coy, it appears he really wasn't contacted and when he eventually was, circumstances simply didn't fit.

"Crisis on Infinite Earths" begins Sunday, Dec. 8 at 8 p.m. ET/PT on Supergirl, then continues in Batwoman on Monday, Dec. 9 at 8 p.m. ET/PT and in The Flash on Tuesday, Dec. 10 at 8 p.m. ET/PT. After the winter hiatus, the crossover will conclude on Tuesday, Jan. 14 in Arrow at 8 p.m. ET/PT and in DC's Legends of Tomorrow at 9 p.m. ET/PT.