2007's I Am Legend, starring Will Smith, changed the vampires from the novel into more zombie-like creatures called Darkseekers, making the movie worse as a result. While using the title of Richard Matheson's novel suggested that it would be a more faithful adaptation than previous versions - 1964's The Last Man on Earth and 1971's The Omega Man - changing the creatures completely altered the entire point of the story, especially the ending.

Matheson's I Am Legend book ends with Robert Neville being executed by the vampires for crimes he committed against them, noting as he dies that he's the boogeyman to the vampires instead of vampires being the boogeyman to humans. This is starkly different to the I Am Legend movie ending, in which Neville sacrifices himself to save two others - Anna and Ethan - by blowing up his laboratory with a grenade, presumably killing every Darkseeker inside as well. It was certainly a more Hollywood type of ending, but one that was noticeably different from the novel. This is partly because I Am Legend portrayed the Darkseekers as mindless, zombie-like creatures, a direct contrast to the novel’s intelligent, human-like vampires.

Changing I Am Legend's creatures - which were created by the virus outbreak in the movie - made adapting the book's ending impossible, as the Darkseekers showed almost no signs of heightened intelligence earlier in the movie. I Am Legend originally had an ending closer to the book's, but that was changed after negative reactions from test audiences. In the original I Am Legend ending, Robert Neville discovers that he had captured the significant other of one of the vampires’ leaders. He then realizes that his attempts to cure the monsters looked less like medical research and more like torture. So, he releases the Darkseeker that he captured and escapes with Anna and Ethan, unsettled by what he just discovered.


The thing is, I Am Legend isn't supposed to refer to him being a legend for the remaining humans, as the final cut shows, but rather to him being a legend to the Darkseeker, being the monster that haunts their nightmares. Had the I Am Legend movie portrayed the Darkseekers more like the vampires of the book, this would have been a much easier idea for audiences to go along with. It would still be a downer ending, as Neville happens to come across as a monster, but that change would at least make it fit more logically in the film.

This flaw isn’t unique to 2007’s I Am Legend though, as it's something that's also been done in the other two adaptations, The Last Man on Earth and The Omega Man. All three versions made the “vampires” into more mindless creatures and changed the original ending substantially. It most likely has to do with the desire to make lead characters “likable”. If Neville is doing experiments on intelligent, human-like creatures, he becomes much more unsettling to watch. The solution? Make them less human. It makes sense but misses the point of the story.

By changing “vampires” to the mindless “Darkseekers”, I Am Legend breaks the main twist that makes the novel more than just another sci-fi story. While a more faithful version of the original ending was filmed, it was rejected, not just because it was a sad ending, but also because it didn’t make sense given how the Darkseekers were portrayed in the rest of the movie.