Answer: Molly Weasley
More information: Molly Weasley is not only Harry's mother-in-law but also an accomplished witch.
Answer: Death Eaters
More information: Lord Voldemort's most-devoted followers are referred to as Death Eaters.
More information: Quidditch is the famous sport resembling soccer yet played with broomsticks in the Harry Potter universe.
Answer: Game of Thrones
More information: Natalia Tena also stars as Osha on Game of Thrones.
Answer: Petunia Dursley
More information: Petunia Dursley is Harry Potter's aunt and was his guardian upon his mother's death.
More information: Harry Potter is a half-blood, since his maternal grandparents were Muggles.
Answer: Order of the Phoenix
More information: Albus Dumbledore founded the Order of the Phoenix in response to the threat posed by Lord Voldemort and his followers, the Death Eaters.
Answer: The Sorting Hat
More information: The Sorting Hat is a magic hat that decides which of the four Houses Hogwarts' students belong to.
More information: There are four Houses at Hogwarts, one named after each of its founders.
Answer: Salazar Slytherin
More information: Logically the answer to this question would be Salazar Slytherin, upon whom Slytherin House is named after.