Glenelg is an obscurely referenced (in the comics) friend of Breshvic Penicillin's whom the other Revengerists find to be quite weird. This is really saying something, since all of the Revengerists are demonstrably quirky in their own ways, some outright freakish. Breshvic thinks Glenelg is hilarious and cool, despite being completely unlike any other of his friends, cohorts or teammates he also think is hilarious and cool. Breshvic even allows him entry to the super-secretive Revengerist Compound, though it is unstated if Glenelg is considered a Revengerist, is even an Awesome, or has any powers.
Breshvic's girlfriend has never met Glenelg, and is not convinced that he exists; she believes he is a figment of Breshvic's twisted imagination allowing him to make up fanciful stories, (which he of course also does). This theory is backed up by the fact that he has changed or butchered Glenelg's name on various occasion, calling him Glenegg, Gelberg, Grüthbarg, or any other words that sound made up. The Revengerists, however, have met Glenelg who pronounces and spells his name differently each time -- adding to their consternation.
When asked, the other Revengerists cannot pin down exactly what it is about Glenelg that they do not like, or specific examples of why he is weird and creepy.
Richard C. Hoagland is convinced that Glenelg is proof that aliens exist and have complex cities and civilizations on Mars and the moon, and that NASA is covering up their war crimes.
Most people in the real world find Glenelg unsettling and off, to say the least. But Glenelg has never been seen committing any crimes. Glenelg, in fact, has never appeared on film or video at all.