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How would you feel about Madelyn Cline as Supergirl?
Well she obviously looks the part, if that means much with certain characters anymore. But I'm not sure I've seen her in anything before so I don't have much of an opinion on her as an actress. It would make sense to introduce Kara in Superman: Legacy though, even if it's a post-credits cameo.
Anyone know where I can find those Supergirl redesign concepts that includes one with red pants?
For when my rants on the forums just aren’t enough: https://thevindicativevordan.tumblr.com/
Do you mean these?
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If you search for Jorge Jimenez Supergirl design there are lots of hits, including in some of his tweets. Sometimes he calls them "discarded designs" but most of them were used at least once.
But maybe you're thinking of something else.