The two characters are going to interact with each other so to make this story/short film/advert more effective i'm going to try and create very different characters. In this case i'm attempting to make the Gorilla look angry and depressed and even scary with the small girl cute and darling in comparisson. Gorillaz already springs to mind for references to create a scary gorilla as these seen in the cemetary scene in their music video 'Clint Eastwood'. In that video lots of Gorillas rose from the earth and generally looked pissed off.

This image isn't from the video but is drawn like these in the vid.