A neuralyzer, sometimes spelled as neuralizer, is a device seen in the Men in Black franchise. It is one of the signature tools and considered standard issue employed by the Men in Black. It is a device about the size of an average cigar tube that gives a bright flash which erases the memories of the past hours, days, weeks, months or years, depending on the chosen settings. It first appeared in the first issue of the comic book series, and has appeared in all three films, and the animated TV show.
In the comic books 
The device in the comic books was referred to as a 'neurolyser'. This is also where the concept of using Ray-Ban sunglasses was introduced. It is seen more in the shape of a flashlight than a cigar-like shape made popular by the films. It does not simply erase memory like the movie counterpart does. In the comic books, the neurolyser is a device used for manipulation and control. When neurolysed, a witness is simply hypnotized and does what ever Agent Kay or Jay wants them to do, such as provide information, believe a lie and/or pass that lie along as fact.
In the films 
A neuralyzer wipes the memory of a target or witness, putting them under a hypnotic state, making them susceptible to suggestion and implantation of false memories. The length of memory erased can be changed using buttons and dials. There are different neuralyzer models with different button and dial configurations. These buttons or dials can be set accordingly to the amount of time needed to be forgotten. The device produces a noisy, camera-like flash. The agents implant new memories in place of the old ones.
In order for the agents to not be affected by the flash, they wear Ray-Ban sunglasses that reflect the rays. After being neuralyzed, the agents have about 30 seconds to supply new memories to replace the ones they've just erased. If there are more witnesses to neuralyze, or if they are pressed for time, a special team is sent in to supply memories.
After being neuralyzed, the witnesses forget the events that are meant to be removed from their memory. But these can still be familiar to them, and the witness sometimes gets déjà vu, as when Dr. Laurel Weaver (Linda Fiorentino) gets déjà vu when meeting Agent J (Will Smith), although her memories of their first encounter were neuralyzed.
A deneuralyzer, only shown in the second film, is a special device that reverses the effects of a neuralyzer. The deneuralyzer takes up a small room in the second film.
In addition to witnesses, the neuralyzer is also used on MiB agents who retire, resign, or are fired, and also on trainees who are rejected.
Changes to the neuralyzer have been featured in the films. In the first movie, the color of its eye was red. This was later changed to blue in the second film. It remains blue in the third film, although the design of the neuralyzer itself is different. In the first movie, the protagonist Jay calls the neuralyzer the "flashy thing" and dislikes the idea of using it and when he has to use it, believes that they should supply the victims with the best memories possible rather than Kay's mundane and depressing memories. He only used it once at the film's end when Kay asks him to neuralyze him with it.
In the second movie, he used it more impulsively and was even attached to it, to the point of acquiring a reputation for neuralyzing other agents (although he attempts to justify his neuralyzation of Agent T - citing Tee's emotional breakdown in a public place, claiming that Agent L "doesn't count," as she wanted to return to her old life and original job at the city morgue). The agents also installed the neuralyzer in many places, like in Jay's car and The Statue of Liberty.
In the third film the original neuralyzer is seen. It is a large contraption that requires strapping the subject into a platform that is then inserted inside the neuralyzer. Later, the young Agent K (Josh Brolin) is seen with an early portable neuralyzer attached to a battery pack that is clipped to his belt.
In the special episode of Sci-Fi Saved My Life dedicated to the Men in Black, experts in the episode said the neuralyzer has a chance of being built in real life. Emotional contact like traumatizing events can be erased, much easier than other memories. Light flashes erasing memories are plausible. Experts say that brain cells can be knocked out or killed by light, perfectly erasing those memories.
The neuralyzer has gained popularity outside the franchise. Sundance Channel[disambiguation needed] ranked it No. 4 on its list of "Top 10 Film Inventions We Wish Were Real," saying that the silver pen-looking thing with the red light needs to exist in real life. Top10Kid.com ranked it at No. 7, saying "The uses of eliminating someone’s memories are endless, especially if you are prone to screwing up a lot." MSN puts it "The greatest fictional inventions of all time."
The neuralyzer also appeared in a special segment of How Stuff Works: Sci-Fi Saved My Life dedicated to the MiB franchise. A remake of it is available in the Android Market complete with sounds and a flash.
In popular culture 
In The Simpsons episode "The Fool Monty," when Smithers leaves Vice President Dick Cheney's employment to return to working for Mr. Burns, Cheney zaps him with a neuralyzer. It appeared again in The Simpsons comic No. 178 entitled "The Thingama-Bob from Outer Space," in which Sideshow Bob is taken away by a man wearing a black suit and sunglasses who promises him that he won't remember anything of what has just happened. It also appeared in the Family Guy episode entitled "From Method to Madness," in which Lois Griffin uses it on Chris when he cannot stop saying "boobies" after meeting a family of nudists.
- Ray-Ban website
- Sci-fi saved my life
- Sundance Channel
- MSN news
- Discovery Videos
- Neuralyzer (Flashy Thingy Memory Eraser) for Android