The "Odd Couple" movie and television show were popular. They portrayed two extremes. An compulsive neatnick and a slob who didn't notice the rotting banana under the dirty clothes in his bedroom.
Write a scene with two characters with opposite personalities. It doesn't have to be clean verses messy. It could be anything. Energetic/lazy, big eater/picky eater, bold/fearful...you pick them. Here's the key; be sure to show it.