Imaginary friends are there to be at your side, or to be the dark expression of inner thoughts.
Mr. Someone used to be somebody's friend a long time ago, but they had a falling out. Now he looks around to find new friends, but he always manages to turn kids into angry, misanthropic misfits. If only he and his original kid can patch things up. (this was an anonymous friend's idea) EDIT: Second version uploaded
Fluffy Sunshine is the very definition of cuddly and wonderful. Soft and inviting and ray of light in a dismal world for Sarah Rose.
Lord Stabhands is nothing but dark angry thoughts. He eats other imaginary friends for breakfast, also lunch, and dinner... and brunch, and as a snack. He's a dark enabler and manipulator supreme, feeding off of his kid's negativity.
Just some fluff for some character ideas.