Here are a couple of errors I picked up of costume cards C19 and c20 where the material has put in the wrong respective card, the normal cards are shown next to them.
C19 and C20 normal and errors

Maybe an attempt to make them more collectible? Seems to have worked! lol... From time to time I think things like this are just going to happen, and I'm not going to dog on Breygent for it. Neat to see though, so thanks for posting.

I have several "error swatches" on sports cards--I think Upper Deck mostly. Most collectors either did't know, or did't seem to care. As long as the card said it was something, that's what the sports collectors seemed to be interested in. I guess a Peter Forsberg card with someone else's jersey or stick, is still a Peter Forsberg card... who knows. --Chris

I really like them personally. They had been on ebay for months as variantsand I had never bothered to open the page, it was only when I did so I realised what they were. I have 45 costume cards so far from GW3&4 and that doesn't include the SDCC cards. I need three more to complete that section.