Wuthering Heights characters?

I have to do an essay about one of the following characters: Heathcliff, Catherine, Hindley, Isabella, Cathy, Linton or Nelly Dean. I have to compare one of the characters to something else, bird, color, food, flower, animal ect.. Unfortunately, I am stumped. All i have thought of is Heathcliff being a shark because he is cruel, ferocious and people are afraid of him.. I need some ideas to help me get started, PLEASE HELP. thanks(: