Because you like The Master in Doctor Who
Working as a captain in the American Expeditionary Forces and a spy for British Intelligence, Steve Trevor wants to end World War I once and for all. See them in DC Extended Universe.
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.
Peter Pevensie shows as much courage as a child king as he did under The Blitz of London. See them in The Chronicles of Narnia.
James Wilson is a compassionate doctor who willingly plays the sidekick. See them in House M.D..
Xander Harris' life motto: laugh in the face of danger and then hide until it goes away. See them in Buffy the Vampire Slayer.
Marlin navigates through shark-infested waters, angry anglerfish, a jellyfish bloom and hungry whales to search for his son. See them in Finding Nemo.
Ofelia is face-to-face with the deadliest creatures of the underworld and completely unafraid. See them in Pan's Labryinth.
For Morgana, sometimes wanting to do the right thing can led you down the wrong path. See them in Merlin.
Ultron is security software turned evil mastermind. See them in Marvel Cinematic Universe.
Extremely violent and loyal, Sandor Clegane is called the Hound for a reason. See them in Game of Thrones.