An animation goof is possible, like a pause at this moment to see a character with an extra finger maybe. It's not like it was part of Yu's jacket that wasn't colored in right as the scene was made, rather something intentionally added. But hey, intriguing for images and conversations like this so yes XD
Another account was the founder of the wiki (wiki fun facts!) yet all wikis are group efforts made and maintained by everyone, even you if you would like to improve articles with official content!