This exercise is something that can be a lot of fun, but especially useful if you’re designing a cast of characters, and find they’re becoming too similar.
It’s fairly simple: Start with a single character’s design, then move on to a second that contrasts the first, so they’re almost opposites of each other. This includes elements like the shape language, size, color, proportions, and expression.
Opposites aren’t necessarily too hard, but now comes the first difficulty: Your third character should now be unique from the other two, but you can’t rely on opposites anymore.
Finally, the fourth character will perhaps be the most difficult to make to stand out from the other 3.
What can make these characters stand apart from each other? This video goes into some ways that can help.