An early episode of Steven Universe, "Watermelon Steven" (S1:E34), revealed a new power of Steven's: to create living, semi-intelligent, autonomous creatures from watermelon seeds (plants).
These creatures were affectionately called "Watermelon Stevens." The gems fought with them until one of the creatures "Baby Melon" sacrificed itself to stop the battle between the Gems and the Watermelon Stevens.
Steven sent the creatures away to have their own lives elsewhere.
My son's question is: What sustains them? Steven's (Rose's) magic made them but why do they keep moving?
Are they gem creatures like the ones that get bubbled in the basement of the temple?
Most magical things stop after the Gems stop concentrating on them, so why are the Watermelon Stevens able to keep moving and even create new versions of themselves?
Why are the Watermelon Stevens so kind and decent (except when they went to war against Malachite)?