Prompt 3: tell me why they act so childish
This character can be childish in your eyes, or in the eyes of other characters. What do they do that makes them seem so childish? Why won’t they stop acting this way? Or they could turn out to be actual children in disguise? 
Mine:
In Lunar Heart, Shadow Bound, Deel acts childish despite looking like a twenty-something-year-old Human. He’s often loud and he doesn’t understand boundaries. He also makes very silly jokes and laughs at them himself. He has huge mood swings and will also have meltdowns in public. He’ll whine for things like a child does.
Actually, Deel isn’t an adult. Many years ago, a Kattaluna child died and during illegal resurrection, his soul split into two. One is the child that died (named Deel) and the other is the adult that lived on (named Daero). The Kattaluna body was disguised as a Human for protection to live among Humans.
Deel, being the soul of the original child that died, could take on the body whenever he wanted and be loud and annoying. The other one, the adult, Daero, is weaker and grows to resent being there for the ride and starts to develop on his own, learning magick and becoming an individual. He acts like Deel’s serious big brother.
Deel is stuck in child years for eternity, and Daero will continue to grow older because he has the adult side. There is no way the souls can separate.