Because you like Fred Mertz in I Love Lucy
Bella Swan thinks of it as her job to help her parents and protect her friends, even though it often ends up the other way around. See them in Twilight.
Jacob Black is the boy next door who's also the wolf next door. See them in Twilight.
A 100-plus-year-old who looks like a dreamy teenager, Edward Cullen warns girls to avoid him, which makes them want him even more. See them in Twilight.
Abandoned by her parents, Rey made her living selling scrap metal and got used to being her own friend and teacher. See them in Star Wars Series.
Yoda is wise, patient, and capable of kicking ass. He's done his best to mentor young Jedi and protect the balance of Light and Dark. See them in Star Wars Series.
Ponyboy Curtis is a "Greaser" on the surface, but he's a sensitive poet underneath. See them in The Outsiders.
Albus Dumbledore oversees the most unsafe school in recorded history, with Dementors and giant arachnids run amok. See them in Harry Potter Series.
Hannah Baker is a buoyant spirit broken by the cruelties of high school. See them in Thirteen Reasons Why .
Kat Stratford is part of the "out" crowd and proud of it. See them in 10 Things I Hate About You.
Eren Jaeger will erase the Titans from this world until not a single one remains. See them in Attack on Titan.
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.