The Fluttercat was a Noble Feline with prime wings (male) or butterfly wings (female). It was released prior to The Second Dreaming Part 1 as a freebie avatar, and could be used after this by players who had purchased the required Digos. Wings are now able to be used on all anthropomorphic Digos.
This avatar can still be used in dreams through species numbers, but it's recommended that players use wing type DS for further customization. A Fluttercat can be rented in Furrabian Nights at the Costumes Stall, but it's unknown whether the actual species or wing types.