Based on the creatures from the Gremlin movies featuring the little fuzzball named Gizmo who is taken cared of by a chinese guy, ends up in the hands of a teenage boy.

The boy recieves the rules of taking care of this creature:
1. No sunlight as it will kill them. bright light scares them. Avoid camera flashes and shade your lamps.
2. No water even if he wants a drink.
3. Never let them eat after midnight. It's the most important rule.

And he ends up breaking the important rule and hell breaks lose because these fuzzy creatures can turn into reptilic or amphibiotic creatures known as Gremlins which theoretically are evil in nature.

- - -

So this mogwai, while isn't inherently the good type (Mogwai are inherently evil, their good-natured trait is recessive) but he was given a chance at life when he met a talented wandering musician. This eventually lead him to play music and channel his evil intentions towards musical expression. I'm not really sure on the mowai/gremlin life story entirely but that is the idea.

The hand gesture is a try at Devil horns. He has three fingers so...