The Harry Potter movies introduced just two houve-elves during their run. Dobby first appeared in The Chamber of Secrets, attempting to stop Harry from returning to Hogwarts, while Kreacher then cameoed in The Order of the Phoenix. Both characters were important in their own right, helping the Chosen One in his quest to destroy the Dark Lord. However, due to the huge amount of details in the source material, not everything could be included on the big screen.
There was no mention of SPEW, short for Society for the Promotion of Elfish Welfare, and numerous other moments from the books weren't shown either. In fact, there are many omitted house-elf moments that only fans of the novels, rather than the blockbusters, will be aware of.
The Aftermath Of Dobby's Trickery
In the second movie, Harry meets Dobby at Number 4 Privet Drive. The loveable, if slightly irritating little creature then reveals he's there to stop the Boy Who Lived from returning to Hogwarts, having grown aware of a sinister plan involving his master Lucius Malfoy and Lord Voldemort. He gets our hero in trouble at his family home, with the Dursleys placing bars on his windows and deciding to keep him prisoner.
The Chamber of Secrets does miss out on all the aftermath, however. Harry receives a letter from the Ministry of Magic warning him against using magic, wrongly believing he cast a hover charm in front of Vernon, Petunia, and Dudley. Petunia ends up having to comfort Mrs. Mason, who has cake thrown over her head, and it's a dire evening for everybody involved.
Winky At The Quidditch World Cup
The Goblet of Fire introduces an elf named Winky, who is missing in the movie of the same name. She works for Ministry of Magic employee Barty Crouch Sr - but is axed from her job after she's accused of casting the Dark Mark at the Quidditch World Cup with Harry's wand. This is actually done by Barty Crouch Jr, something the villain's father is aware of, but Winky's owner doesn't care and she's ruthlessly relieved of her duties.
Winky is crushed after her master's decision, sobbing tears of sorrow. She ends up getting a job at Hogwarts courtesy of Dobby and Albus Dumbledore but, instead of being happy about this, she doesn't take to it well...
The Kitchens
Winky is able to get a job in the Hogwarts kitchens, with Dobby - being the nice individual he is - putting in a good word. However, when Harry, Ron, and Hermione visit in their fourth year, they find her drunk on Butterbeer. Mr. Crouch's behavior has broken her poor heart and the main trio do all they can to cheer her up.
Harry and Ron love their time in the kitchens, with the elves bombarding them with food. Hermione, not so much, however, with Hogwarts' brightest student shocked at how happy they are, despite working for no money whatsoever.
SPEW
SPEW isn't really an isolated incident during the Goblet of Fire book, but more of an ongoing theme. Hermione is appalled when she learns of the existence of House Elves in the Wizarding World, assuming that they must be miserable and need her to campaign to save them. She attempts to free as many as possible by disguising clothes around Gryffindor Tower, knowing they clean the premises at night. She also creates badges for Harry and Ron to reluctantly wear, while also campaigning hard for better treatment.
She means well, but the elves are insulted by her gestures. They don't want to serve extra food to Harry and Ron again and the Boy Who Lived ends up discovering all the clothes she's made are taken by Dobby, who is the only person willing to give Gryffindor Tower a good scrub. The sight of him wearing multiple hats, scarves and other items was funny to read in the book - and would have been amusing to see on the big screen.
Stealing Gillyweed
In the fourth movie, Harry is in trouble as the second task of the Triwizard Tournament nears. While Cedric Diggory had helped him roughly discover what his mission will entail, he can't find a way to breathe underwater for an hour. Fortunately for him, Neville Longbottom is nearby and he ends up stealing some Gillyweed for the Boy Who Lived to use - although, as you'd expect, isn't entirely confident his plan will work.
Things are different in the book, though. It's actually Dobby who does this, stealing the plant from Severus Snape. It seems as though Warner Bros opted to change things up because Dobby would potentially have been pricey to use, especially only for a few seconds.
The Room Of Requirement
Out of all the places inside Hogwarts, the Room of Requirement is arguably the most magical. It will do anything you please and is used by Dumbledore's Army in both the Order of the Phoenix and Deathly Hallows: Part 2 movies, while also popping up in the Half-Blood Prince when Harry is forced to hide his illicit potions book, having come precariously close to killing Draco Malfoy.
Again, it's discovered by Neville in the film. But, in the book, it's Dobby who tips Harry off. He later decorates it with Christmas baubles besing his face, and he's first on the scene to warn them when loathsome Defence Against the Dark Arts teacher Dolores Umbridge discovers their secretive lessons.
Kreacher's Lie
In the Order of the Phoenix book, Harry uses Umbridge's office to reach out to Sirius Black at 12 Grimmauld Place after he sees a vision of his godfather being tortured by Lord Voldemort inside the Department of Mysteries. The Boy Who Lived's worst fears are confirmed when Kreacher informs him Sirius isn't there, with Harry then taking this as his cue to race to his godfather's rescue.
Unfortunately for Harry, this is a lie. Kreacher, loyal to anybody who shows him the slightest bit of love and affection, actually injured Buckbeak to ensure Sirius wouldn't be around by the time Harry comes calling. What's tragic about the whole thing is that Sirius, after traveling to save Harry from Voldemort, is ruthlessly murdered by Bellatrix Lestrange.
Kreacher At Privet Drive
Petunia Dursley is a meticulous person. She likes Number 4 Privet Drive to be spotless and sparkling, regularly going out of her way to make it the nicest property on the street. However, in the Half-Blood Prince, she's left repulsed when Albus Dumbledore summons Kreacher to the premises after the Hogwarts headmaster decides to take Harry away for the remainder of the school holidays.
Dumbledore does this because the elf is needed to know whether Harry is now the owner of 12 Grimmauld Place or not. The Chosen One tells Kreacher to 'shut up' and he's immediately silenced. Dumbledore then proceeds to slam the Dursleys for the way they've treated Harry over the years - which is another scene that would have been entertaining to see play out.
Hokey The House Elf
During Harry's sixth year at Hogwarts, he spends a fair bit of the school year taking trips down memory lane with Dumbledore. Together, the pair delve deep into Lord Voldemort's past in order to get a clearer picture as to how to defeat the Dark Lord. Not all of these flashbacks are included in the Half-Blood Prince movie, though, meaning fans never got to see Hokey the House Elf.
Hokey works for a lady named Hepzibah Smith, who is charmed and then murdered by Tom Riddle during his time as a shopkeeper at Borgin and Burkes. The student, who would grow up to become Voldemort, then frames her servant for his despicable crime. Hokey tells the story to Dumbledore at a grand old age and it's unknown what happened to her after she's accused of manslaughter. Her information is vital, helping pave the way for Voldemort's ultimate destruction.
Kreacher's Redemption
Kreacher appears again in the Deathly Hallows: Part 1 movie. However, he should have made a fleeting cameo in the second part.
The house elf is present at the Battle of Hogwarts, leading creatures of his own kind against Voldemort and his horrible Death Eaters. Furthermore, he wears the fake locket given to Harry in his sixth year while participating in the fight. It's a moment of redemption for Kreacher, who ends up surviving the battle and living to serve the Boy Who Lived for the remainder of his days.