Dobby is one of those characters that people either love or hate. He is one of the House Elves that make an appearance during the Harry Potter series, and, though he is one of many, he is one of the few that’s actually given a name in the series.
It may come as no surprise to hear that the movies actually left quite a lot out about these helpful little creatures. They were rather limited on time, after all. And some of the things they didn’t leave out, they changed.
Winky
Let's start this list with the most obvious change; the character they left out. Winky is one of the few named house elves in the series, yet she doesn't make the cut for the movies. To be fair, it would have taken some time to introduce and explain her. So, they were probably trying to save time more than anything by not including her.
Winky is the prime example of a house elf that doesn't want to be free. In her mind, being handed clothing means utter and complete failure, and it's not something she was ever able to really get over. She spent the time after her firing—for that's really what it was—getting drunk on Butterbeer and in general making the other Hogwarts house elves feel ashamed of her.
Kreacher’s Behavior & Backstory
Kreacher lost a lot of his backstory in the transition from book to movie, and that affected his behavior, too. In the books, it's explained that Kreacher was so painfully loyal to R.A.B., aka Regulus Black, as well as the rest of the family. Voldemort had used Kreacher to set up the protection for one of his Horcrux, never expecting Kreacher to survive it. Later, Regulus came back for said Horcrux. But instead of forcing Kreacher to drink the vial liquid as Voldemort had done, Regulus himself drank it, ordering Kreacher to take the Horcrux and destroy it, thus dooming himself in the process.
This left Kreacher with a complex series of emotions. Adoration, guilt—both for failing to protect his master, and survivor's guilt—grief, and so much more. When Harry gave Kreacher's the false locket that Regulus had created, it turned the tide of emotions for the little elf. He went from loathing Harry and friends into almost liking them. He was kinder because he had been shown kindness.
The Battle of Hogwarts
All of Kreacher's backstory, as mentioned above, came to a head in the Battle of Hogwarts. Here, Kreacher took it upon himself to gather the house elves of Hogwarts and bring them into battle. His war cry implied that he was doing it in honor of Regulus, the human who gave his life for the cause. The human who valued Kreacher's life above his own. None of that actually made it into the movie, which is a crying shame. It showed how complex these little creatures can be despite how most of society looks down upon them.
The Hogwarts Elves
Speaking of the house elves of Hogwarts, did you even know that they existed? The movies basically glossed over this entirely. The movie sort of implies that they exist because of Dobby being around, but that's about the extent of it. But seriously, think about it. How could a castle of that size, full of that many students and professors, possibly function without a little help?
The help came in the form of house elves. Hogwarts had over a hundred of them—not that we ever got an accurate count. They would prep the food, clean the dorms, the works. Though they stopped cleaning the Gryffindor dormitories once Hermione started leaving little knitted hats and socks under trash and other items. Harry and crew interacted with the house elves on more than one occasion, which is how they knew that Winky had been added to the staff alongside Dobby. The latter two were the only paid house elves on staff, something which the rest of the house elves found to be disgusting.
Their Contentment
Despite what some believe—looking at you, Hermione)—house elves are shockingly content with their lives. Well, for the most part. House elves that deal with abusive masters, like Dobby, are probably less inclined to feel content. But they are proud and would rather not be freed or, in their minds, fired.
That's the whole reason the clothing thing works for them. House elves consider their lack of clothing to be a sign that they are content with their family and wouldn't want to be doing anything else. This all leads to the Hogwarts elves. We know that they could get paid if they wanted to—Dobby and Winky are proof of that. They could also get days off, if they wanted. But even Dobby didn't want too many vacation days. Proof that there is a limit, even where that is concerned.
S.P.E.W.
S.P.E.W., aka the Society for the Promotion of Elfish Welfare. This is an organization—if you can call it that—that Hermione Granger started. She coerced her classmates, mostly Ron, Harry, and Neville, to join. The whole goal is in the name; getting better care for elves.
This is something that was cut entirely from the movies. Even though it became the foundation for Hermione's career, in a sense. Her realization of how house elves were treated forced her to acknowledge that the magical world isn't perfect and that somebody would need to make some dramatic changes, else they would never happen. We don't really know how the house elves felt about Hermione's organization. If the ones working at Hogwarts had an opinion on the matter, they kept it to themselves.
House Elves Are Not Allowed to Have Wands
In the world of Harry Potter, it is illegal for all magical creatures—outside of witches and wizards, that is—to own wands. That includes house elves. In fact, based on the reactions shown in Harry Potter and the Goblet of Fire, it likely isn't even legal for a house elf to be in possession of a wand, regardless of the reason.
This was hinted at later in the books as well when they're talking with a goblin about goblin rights—or the lack thereof. However, none of this even makes it into the movie, even though it would have been a quick way to show the inequality at play.
Loopholes
House elves are actually quite good at finding loopholes. There are two famous examples of this, both of which actually making it into the movies. The first is when Dobby went to warn Harry Potter not to return to school in the second film, and the latter is when Kreacher helped set up the situation which ultimately led to Sirius' death.
Later in the books, Harry uses Kreacher as a spy. But he's very careful in his wording, being careful to leave no loopholes available. That's because, if a house elf is unhappy with their house, they'll likely to the bare minimum of their orders and no more. Unlike a happy house elf, who will go above and beyond. Worse, an unhappy house elf will likely look for any loopholes in their orders, to help circumvent doing something they'd rather not do. Though sometimes, as with Dobby's example, using the loophole results in them having to punish themselves.