They are a group of Ataru's classmates and so-called friends, all of whom are pathetically infatuated with Lum. Lum's Stormtroopers, Lum's Fan Club, Lum's Guards..Call them what you will. These four average high school boys have one unifying goal: To assure Lum's happiness. In doing so, each of them keep vainly hoping they can win Lum's heart.
There's four members to this cast of miscreants. There's Perm, the gawky boy with puffy hair, Chibi the little twerp who's always being beat up, Kakugari the large bully type who's almost always beating up on Chibi and then the one with glasses, their leader Megane. They're all best friends, but wouldn't hesitate to stab each other in the back if Lum is involved. All of the boys want Lum, but it would seem that Megane is the only one who truly loves her. He would go through hell and back for her, if only she hadn't fallen for that fiend Ataru.
Megane is highly philosophical and intellectual yet he is also an obnoxious loud mouth, and I mean loud. He is prone to bombastic speeches and temporary fits of insanity that bring attention to himself. Screaming at the top of his lungs whenever he gets the least bit emotional. He's a characiture of a crazed, obsessed otaku taken to an extreme.
Megane takes his love for Lum very seriously. He has dedicated his life to admiring her. He even has to keep the other three in line since they often waver in their dedication to Lum. Painfully he knows that Lum only has eyes for Ataru, but he can bear it because her happiness is paramount to him.
Megane is also somewhat of an amateur film producer. On a few occasions he has tried to create movies, always with Lum as the heroine. Megane also has build a homemade mobile combat suit which he sometimes wears to do battle. He still gets the tar beaten out of him, but at least he can look cool in the process.
Although they are important characters in the anime, Lum's Guards were virtually non existant in the the manga. In fact they only show up as random classmates in the first couple of UY volumes and disappeared from the cast when Takahashi started to take UY in a different direction. Megane and the others seem rather to be in the show to act as the voice of the directors (putting themselves and their own sensibilities into the show), and because Megane's voice actor is such a scene stealer, that they eventually decided he would become a central figure in the show. Megane is used so much, that he practically compeats with Mendo for screen time. Purists of the original comic might dislike these guys for how they mess up the original dynamic and take some of the focus away from the main characters. But in the end, Lum's Guards are entertaining, and they add a lot to the show.
Notes about the name
The names of the four guys describe their distinguishing features. Megane means "glasses" Perm (pronounced in Japanese as paama) is of course in reference to his frizzy hair style. Kakugari means "buzz-cut" Chibi means "puny" or "runt"
Voices: Chiba Shigeru, Issei Futumata, Akira Murayama, Shinji Nomura
Megane is played by the popular Chiba Shigeru (who kind of looks like an asian Malcom McDowell), one of the most widely heard voices in anime. He's been in everything. Some of my personal favorite roles of his include Yotsuya of Maison Ikkoku, Shige from Patlabor and Kuwabara from Yuu Yuu Hakusho.
Chibi's voice is done by Issei Futumata who I swear doesn't usually look as skinny and nerdish as he does in this picture. Futumata does the voice of Yuusaku Godai of Maison Ikkoku as well as Mikiyasu Shinshi of Patlabor, and many miscellaneous small parts in UY, Ranma and more.
seiyuu is Akira Murayama. Has had a lot of lesser roles, but was a featured
player in Esper Mami, Captain Tsubasa and Master Keaton to name a few.
Kakugari's seiyuu is Shinji Nomura who played Yoshiichi Aihara on the popular sci-fi Uchuu Senkan Yamato.