Minor 'Harry Potter' Characters Who Do Something Essential In The Books

Colin Creevey is a real annoyance to Harry early in Chamber of Secrets for his tendency to photograph him all the time. But Colin's picture-taking turns out to be a blessing in disguise when Colin's petrification becomes a valuable clue for Harry.

Harry pieces together the events that have taken place and realizes Colin survived the basilisk because he saw the snake through his camera lens. Plus, Colin's status as a Muggle-born is part of a pattern of children with nonmagical parents being targeted, which helps Harry figure out what the basilisk's motives are.

Colin is thus indirectly responsible for Harry's eventual victory against the basilisk.

The Wizarding World lives in constant fear during the Second Wizard War because Voldemort controls the news. Lee Jordan and Fred and George Weasley, however, are responsible for bringing legitimate news to the public through the Potterwatch radio show. Lee relays the current happenings, making sure to use the assigned aliases of the correspondents to maintain their anonymity and safety from Voldemort's followers.

The Wizarding community uses Potterwatch as a morale-booster and platform to encourage anti-Voldemort efforts.

During the Battle of Hogwarts, Harry, Ron, and Hermione are stricken with grief by the loss of their friends and find themselves unable to create Patronuses. The trio are swarmed by dementors and about to be offed when Patronuses conjured by Ernie MacMillan, Luna Lovegood, and Seamus Finnigan come to their rescue.

Ernie was never part of Harry's inner circle in school, but turns out to be one of his saviors when it counts the most. Ernie's Patronus takes on the form of a boar that drives a significant number of dementors away. His intervention with Luna and Seamus then motivates Harry into regaining his fighting spirit.

Sirius's innocence would never have come to light without Hermione's pet cat Crookshanks. He recognizes Peter Pettigrew as Scabbers the moment he sees him and begins to communicate with Sirius in his dog form at Hogwarts. 

Crookshanks provides Sirius with the information he needs to navigate through Hogwarts undetected, later assisting Harry and Hermione against the Whomping Willow so the two can meet Sirius to learn the truth about him in the Shrieking Shack.

Harry's original intention was to slay Sirius when he believed the latter to be responsible for his parents' demise, which makes Crookshanks responsible for averting a possible tragedy between Harry and Sirius.

After Harry helps capture their fathers in the Battle of the Department of Mysteries, Draco Malfoy, Crabbe, and Goyle plan on ambushing him in the Hogwarts Express. 

Harry would have been outnumbered and caught by surprise had it not been for the presence of Dumbledore's Army members in the nearby compartment: Ernie Macmillan, Hannah Abbott, Susan Bones, Justin Finch-Fletchley, Anthony Goldstein, and Terry Boot.

The D.A. members jump to Harry's defense and simultaneously jinx Malfoy and his goons, knocking them out indefinitely. Harry was likely going to be severely accosted by Malfoy's goons since they were out for retribution, so the D.A. members' intervention rescued him from a painful fate.

Winky the House-elf's grief is beyond measure when she's released from serving Barty Crouch Sr. She becomes routinely inebriated during her subsequent stay at Hogwarts, which disgusts the other House-elves.

Dobby is the only one who takes care of Winky and discovers the Room of Requirement when he seeks a place to store her during one of her inebriated spells. He later relays the existence of the Room of Requirement to Harry, who forms Dumbledore's Army there.