Because you like Moist von Lipwig in Discworld

Aang is already a master airbender and once he learns to manipulate water, earth, and fire, he'll be truly unbeatable. See them in Avatar: The Last Airbender.

Optimus Prime is a shapeshifting sentient robot leading a team of robots to stop evil from taking over. See them in Transformers.

Is there more to life than being really, really, ridiculously good looking? Derek Zoolander thinks not. See them in Zoolander.

Megamind is searching for purpose in a supervillain life without a superhero to fight. See them in Megamind.

Imperator Furiosa is a badass patriarchy toppler. She'll do anything to secure a better, freer future for the women she cares for. See them in Mad Max: Fury Road.

The son of Death has an obsession with perfection and symmetry. See them in Soul Eater.

Newt Scamander is more comfortable with animals than people, even if the animals are super-dangerous magical creatures. See them in Fantastic Beasts and Where To Find Them.

Titus Andromedon will show you the ropes, help you with your problems, and sing at you constantly, whether you like it or not. See them in Unbreakable Kimmy Schmidt.

The poster child for relentless cheer and resilience, Kimmy Schmidt may be an abuse survivor but she's also a lover of dancing and karaoke, candy, and dolphins. See them in Unbreakable Kimmy Schmidt.

You don't teach a class called "How To Get Away With Murder" without knowing a thing or two about getting away with things. See them in How to Get Away with Murder.

Bedside manner is for chumps, not the brilliant Dr. Gregory House. See them in House M.D..

Brilliant, violent, and only a little insane, the Joker doesn't listen to anyone except the voices in his head. See them in DC Extended Universe.