Because you like Clyde Barrow in Bonnie and Clyde
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.
Hiccup Haddock III may be the only Viking nerd in recorded history. See them in How to Train Your Dragon.
Jacob Black is the boy next door who's also the wolf next door. See them in Twilight.
A gentle alchemist who is soul-bound to a giant suit of armor, Alphonse Elric is growing into the responsibility handed to him. See them in Fullmetal Alchemist.
Leslie Knope can accomplish anything, literally anything, with a little grit and help from her office. See them in Parks and Recreation.
Alison DiLaurentis believes you're always better off with a really good lie. See them in Pretty Little Liars.
Tracy Turnblad's got rhythm, and she's determined to share her dance moves with the world. See them in Hairspray.
Frank N. Furter is just a sweet transvestite with some not-so-sweet plans. See them in The Rocky Horror Picture Show.
Poison Ivy is a seductive, venomous botanist laments the fact that there are so many people to kill, yet so little time. See them in DC Extended Universe.