Because you like Nanny McPhee in Nanny McPhee
Usually the life of the party, Laszlo is now seriously planning the vampiric takeover of the New World. Or at least Staten Island. See them in What We Do In The Shadows.
A gifted detective, Rust Cohle is as dark and twisty as any murderer he chases. See them in True Detective Season 1.
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.
Louise Belcher might be just a kid, but she can manipulate just about anyone with a pulse. All in the name of fun, of course. See them in Bob's Burgers.
Ultron is security software turned evil mastermind. See them in Marvel Cinematic Universe.
Ahsoka Tano hopes to be a very powerful and knowledgeable Jedi one day. See them in The Clone Wars.
Count Olaf is a traveling actor, except he can't act and his homicidal tendencies make finding work pretty difficult. See them in Lemony Snicket's A Series of Unfortunate Events.
David Rossi may chase serial killers for a living, but he's more interested in what wine pairs well with tonight's parmigiana. See them in Criminal Minds.
Xander Harris' life motto: laugh in the face of danger and then hide until it goes away. See them in Buffy the Vampire Slayer.
Boomerang is equally skilled at tossing boomerangs and tossing back beers. See them in DC Extended Universe.
Nandor is a relentless vampire who never admits he's wrong, loves glitter, and can't use a tablet. See them in What We Do In The Shadows.