Any card has the potential to have an upside-down back, but obviously it’s a rare thing to occur.
The wailmer/pikachu and mew are that you mentioned are the two that are very commonly upside-down
Thanks! That makes sense. I guess for the sake of clarification - I think we’ll assume that while any card ‘could’ have the upside down back, have there been any other confirmations of such in POP Series 5 other than Mew & Wailmer/Pikachu?
I believe @quuador mentioned in an old post he has seen a Pelipper & Zangoose and perhaps heard of the same for Lugia & Ho-oh. So maybe with Pelipper, Zangoose, Mew & Pikachu confirmed - the question becomes is there upside down versions of Lugia & Ho-oh (and I guess any of the non-holos as well).