Signature Animal Sprites?

[Fish]

I notices that in a few signitures that for their villager wish-list they have similar looking sprites, like this one:
http://i.imgur.com/1b7V830.png

Is this from somewhere?

 

[Gizmodo]

Go here c:
http://welcometoathena.tumblr.com/post/54852487291/animal-crossing-sprites-masterpost

 

[Fish]

Thanks so much ^^