Character Sketchs

So in class we have to make a children's book. it spans over two classes.
so we have to, you know, make characters and a story and stuff. So these are 3 of my 4 "main" characters.
Keep in mind this is still a sketch in my eyes because im going to add simple shading later.

I actually have no names for them so if any of you would like to suggest any, my ears are open.

the main character. the one being focused on is the little red devil looking monster.
Its a male. The black monster is as well.
and i dont know whether to make the cat a boy or girl. So it's just an it right now.