Because you like Casper in Kids
Howard Wolowitz is an engineer whose serious mommy issues somehow haven't dimmed his confidence. See them in The Big Bang Theory.
Kesuke Miyagi is a karate expert who thinks the best way a scrawny high schooler can learn how to defend himself is by washing every surface in sight. See them in The Karate Kid.
Pro tip: the psych ward is not the best place to find a mentor like Lisa Rowe. See them in Girl, Interrupted.
Kara "Starbuck" Thrace will beat you in cards, drink you under the table, then fly circles around you in her fighter plane. See them in Battlestar Galactica.
They say they saved Adam Jensen by turning him into a cyborg, but he's not sure saved is the right word. See them in Deus Ex Series.
Jack Bauer is a terrorist fighter who is scared of nothing and no one. The clock is ticking! See them in 24.
If anyone can stay optimistic and friendly under harsh alien rule, it's Alyx Vance. See them in Half-Life 2.
In the simplest terms, in the most convenient definitions, people consider Brian a nerd. But he's more than that. See them in The Breakfast Club.
Ultron is security software turned evil mastermind. See them in Marvel Cinematic Universe.