Stitches was a regular plushie who sprang to life when a spell turned all Neopets into plushies. They made friends with TDMBGPOP and Buttons, and remained animated even when the spell was reversed. Stitches originally attempted to steal food from the local food shops when they gained life, to see what it tastes like, and continues to have a greedy streak.
Stitches has an owner, who looks like this:
The book in which Stitches appears is an in-universe graphic novel. As such, it is unclear if they ever really existed at all.
