Jellybean is a specially animated plush toy (plush construct) created by Nilla that is powered through affection. The more love and affection Jellybean receives, the more animated and lifelike they become. Without any affection, they return to an inert form.
Jellybean additionally has a benefit of being able to bodymorph themself to better fit desires or wishes of cuddles, often doing so unconsciously (like growing larger in size for someone who wants a large, comforting hug).
These designs and flaws were built into Jellybean to help them serve as a loving and affectionate therapy and comfort toy for others, particularly JB's creator, Nilla. She created Jellybean to help comfort her and accommodate her trouble with maintaining relationships and difficulty in social interaction leaving her with frequent loneliness.