Because you like Ethan Tremblay in Due Date

A benevolent madman with a blue box, The Doctor is traveling through time and space to heal the wounds of the universe. See them in Doctor Who.

John Watson is haunted by his past (who isn't) but he's starting to branch out with some help from a world class detective. See them in Sherlock.

Steve Rogers is a good soldier. But above all, he's a good man. See them in Marvel Cinematic Universe.

Smart, sarcastic, and loyal, Stiles Stilinski doesn't just want to be the sidekick in someone else's life. See them in Teen Wolf.

Severus Snape is a misanthropic potions teacher with a vindictive streak. See them in Harry Potter Series.