Muggles' Guide to Harry Potter/Characters/Arnold

Overview
Arnold is a purple Pygmy Puff, a miniature Puffskein. He is owned by Ginny Weasley.

Half-Blood Prince
Ginny buys Arnold from her brothers Fred and George, at their Wizarding joke shop, Weasleys' Wizard Wheezes in Diagon Alley. He is very fluffy and Ginny describes him as "Really cute." Pygmy Puffs resemble little fluffy balls that roll around, squeak, and come in various shades of pink and purple. Luna Lovegood believes that all Pygmy Puffs sing on Boxing Day

Analysis
Pygmy Puffs are actually rather curious examples of Fred and George's entrepreneurship. The Puffskein, from which the Pygmy Puff is apparently derived, is apparently a reasonably common Wizarding pet. The pygmy puff, a version unique to Fred and George, is made miniature and pastel shaded by some artifice of theirs, and seems designed for tween and teen girls.