I can't seem to find any list of all the Tamagotchi V3 characters. The one I got off the official site does not have them all! :) I looked at the list that -Ra- made for Tama Zone and it had many characters that weren't on the list from Tamagotchi Connection.com
To prove how easy it would be to edit in twins here is my *attempt* at making the twins Patapatatchi and though it didn't turn out amazing it shows how easy it is. https://i10.photobucket.com/albums/a130/Tatter_13/Twins.jpg