Dollotrons were the final result of Lazlo Valentin aka Professor Pyg "perfecting" a person, using identity-destroying chemicals and treatments in a brutal process that left his victims irreparably scarred, physically and mentally. Dollotrons are victims lobotomized into essentially organic robots unable to think or feel anything. This makes them highly resistant to pain and only complete unconsciousness was enough to prevent them from mindlessly attacking their target.
Pyg, after he suffered a mental breakdown that made him utterly deranged, came to believe that people must have everything unique about them removed and/or destroyed if they were to become "better" and "perfect" as he saw it.
As the ringleader of the Circus of Strange, Pyg kidnapped guests of all ages and both sexes during his shows where he used invasive surgery and personality-destroying chemicals to brutally mutilate his victims and "perfect" them into his Dollotrons. Those that he could not "fix" for one reason or another, were killed and thrown out like trash.
Before Arkham Knight Incident
Lazlo Valentin AKA Professor Pyg spent an unknown amount of years luring unsuspecting people into his Circus of Strange, so he could capture them and turn them into his Dollotrons. His severe mental instability caused him to even break deals he made whenever he took hostages, such as when he turned a hostage into a Dollotron prior to the ransom being delivered, and proceeded to do the same to the man who delivered it. Pyg conducted the "perfection" process in an operating theater hidden underneath his Pretty Doll's Parlor beauty saloon.
As Batman points out, these victims are suffering a fate worse than death itself.
Arkham Knight Incident
During the Arkham Knight Incident, Batman found six mutilated bodies strung up around Gotham like hunting trophies of sorts with opera music being played on loop through speakers placed around the bodies and words like "failure", "broken" and "defective" written besides them. Because the brutal process of turning them into Dollotrons corrupted their DNA and destroyed their fingerprints, Batman had to use his Deep Tissue Scanner to look for unique traits that made them stand out in the Missing Persons Database. All the victims had similar traits: troubled pasts, prior surgeries before being kidnapped, had scars on them from accidents and/or traces from the surgeries, genetic deformities, and they all went missing at fairgrounds and parks around the country; all of which were where the Circus of Strange had stopped on its route. Alfred found only one associated name involved with the circus: Lazlo Valentin, who used to lease a beauty salon in Gotham, the Pretty Dolls Parlor, but the lease expired before construction began on Wayne International Plaza. Alfred also warned Batman to proceed with caution, considering Pyg as unhinged, even by Gotham standards
Based on this information, Batman made his way to Pretty Doll's Parlor where the same opera music from before was immediately audible (albeit faintly), raising Batman's suspicion. Making his way to the "staff only" section and breaking through a boarded-off wall, Batman found the entrance to Pyg's operating theater.
Professor Pyg was interrupted during one of his experiments by Batman, who demanded that he release all of his prisoners from his Monster Machine. Pyg refused and turned his Dollotrons upon Batman before joining in the fight himself, throwing knives and cleavers at Batman while singing crazy song lines as the opera music played on, all the while Batman was fighting off his creations. After defeating the Dollotrons, Batman knocked out Pyg and arrested him, taking him to the GCPD Lockup. The victims themselves were also later interred at GCPD.
- What exactly Pyg did to the Dollotrons to corrupt their DNA and ravage their personalities was unknown. In the middle of his experiment, it's seen that he wrapped both their heads and hands in bandages before dressing them in hospital robes and applying a doll mask to their face, and these masks were not removed at the GCPD Lockup. He's also making random cuts and slices into their flesh, but it was unknown what that procedure was supposed to do exactly. The only known procedure was the presumed removal of sexual organs like breasts and male genitalia as seen when the bodies were scanned with the deep tissue scanner and observed scars on the body of the Dollotron that Batman fought after he initially confronted Pyg, which effectively mutilated them.
- While at the GCPD Lockup, the Dollotrons were violently twitching and their condition read: "Terrified".
- It was not explained what happened to the Dollotrons after the events of Arkham Knight, but due to their irreparable condition, it was possible they were killed out of mercy. This can be further expanded as with a recent update, the Dollotrons are not in their cell after the attack on GCPD.