Welling offers that WB initially wanted the Smallville finale to have a big Superman appearance, but Welling was against the idea as he says it didn't fit with what they did in all the Seasons of Smallville.
“Our series finale was supposed to be, in the first act, Clark puts on the suit and flies around, saves Lois on a plane, and does this other stuff,” Welling says. “It was a call that I had with Peter Roth, who is the head of Warner Bros. Television, who’s a good friend of mine and we have a great relationship. I said, ‘That’s not our show, Peter.’ He’s like, ‘No, it’s going to be great,” and I go, ‘Yeah, but just think about what we’ve been doing. If we just jump into that, we haven’t earned it.'”
“We jumped onto this idea that at the end of the show, the idea is that Clark becomes Superman and he’s out there, and we know he’s out there, but we can’t go with him, but that we know and we feel good that he’s out there doing good,” Welling says. “That was what we strove for, and I think we hit it. I liked the ending of the series, because it’s like, ‘Yes, he did it!’ I hope the audience didn’t feel like we didn’t show them something that they needed to see. I felt like we gave them the jumping off point for their imagination as to what could happen.”
Regarding Supergirl, Tom Welling reveals there was talk of having him return there as well; however, he felt his time had passed.
“I know Greg quite well and there had been some discussion, but they’re different worlds,” Welling says. “There was an idea that maybe Supergirl, appearing on that, but it’s such a different show. I’m older now, I don’t look the same. Appearing on that show as Clark Kent or even Superman, for me, I would not want to watch me do that at all. They just have such a different tone. To me, because this is still even a DC Universe, which wasn’t a consideration in the beginning, but Lucifer is still DC, so in some ways it’s one foot in, one foot out, but it wasn’t a motivator for me to join the show. It just so happens that it was connected in that way.”
Hmmm... I'm not sure how I feel about Tom Welling not appearing in the red and blue tights as Superman. On one hand I can agree with what Tom Welling has to say about not appearing as Superman in the Smallville finale. He is right in that Smallville wasn't really about "Superman" per se, but I do know a lot of fans expected something much bigger than what was shown as the entire series was building up to "that" moment. I do feel the ending was fine with Tom opening his shirt and seeing the Superman symbol.
Regarding Tom Welling as Superman on Supergirl, now that would have been something! As Tom Welling is older now, they could have went with a version similar to the Earth-Two or Earth-22 Superman from the comics and Kingdom Come! I can't complain though as I felt Tyle Hoechlin really nailed it as the Man of Steel!