My h/c is that there were other monsters throughout the years in Area 5X that weren't around as long as the four main monsters when Susan was captured, like the Invisible Man. These are my two contributions to this supposed string of short-lived monsters. This is gonna be a LONG post, so fasten your seat belts!
a werewolf from Germany. He was in Area 5X from 1958-1965 and the first monster there.
His abilities as a wolfman were strength, agility, speed, and moderate resistance to physical harm. In this form, he was muscular and tall (almost as tall as Link). But in every transformation, he lost a lot of his human reason and conscience, and whatever he could remember after reverting was like a fog with faded distorted noises. He slowly learned to retain some amount of human reason and conscience but sometimes he couldn't achieve that. The only thing that could kill him was a silver bullet or another wolfman/werewolf. He was very stubborn and oftentimes serious, so he often came across as crotchety and cold to the other monsters. If you were nice to him, he'd warm up to you in due time, even if you didn't speak German. He LOVED music, especially anything that reminded him of home. He learned to play an instrument (probably the piano) at an early age but stopped, so he barely remembered how to play it when he came across one several years later. He oftentimes sang to himself, especially in the years before Link, the next monster, was captured. The Invisible Man couldn't carry a tune and Dr. C largely only hummed something while working, so von Wolfmann was pretty much alone in his endearment for music. As a wolfman, his hands-down favorite food was fresh raw meat. His hands were too large for silverware, so he had to use his bare hands and later on a complementary napkin
He was born and grew up in Bavaria (in modern-day southeast Germany, early 1880s). His former name is unknown. He was bitten by a cursed wolf at the age of 6 and, after accidentally killing 1-2 family members within the first transformation, ran away from home and went to live in the forest away from humanity where he was first bitten. Over the years, he fought off other werewolves/wolf-people in that part of Germany and killed them all by the age of 18 in order to protect humanity (turn of the century/early 1900s) and even found and killed the cursed wolf that killed him, perhaps putting an end to its terror and the terror it caused. He was caught shortly afterwards and placed in an insane asylum, sometimes in solitary confinement off and on. He was misdiagnosed as an epileptic, but after each "seizure", anyone who was in the same room as him would be dead or seriously injured. There was little to no belief that he was actually a wolfman. He escaped after 3 years and in the process was shot and almost died (1910s). This cycle repeated itself a couple times throughout the years (capture, asylum, escape) (1920s-30s). Upon his last escape, he knew what the German government was up to in World War II and tried to stay out of the Nazi regime. Unfortunately, he was found and captured again and used as a means of extermination in a Nazi death camp. He could never forgive himself for that. He escaped during Germany's defeat (1940s), found his way back to his homeland, and lived alone as a hermit (1940s-50s).
In 1958, he was found, arrested, tried (amazingly, had to do it at any time other than a day with a full moon), and sentenced to death for his crimes against humanity (before, during, and after the war), but the USA intervened in his death sentence, took him into custody, and brought him to Area 5X to lock him away from humanity and turn his death sentence into a life sentence. Being 2 miles underground, he was perpetually stuck in mid-transformation: the abilities and height of his full wolfman form but now fully retaining his human reason and conscience. He REFUSED to learn English when given the opportunity, but he was so relieved and a bit happy that he wouldn't be a full fledged wolfman anymore. These final years were some of the better years of his life. But despite being directly away from full moons, he got a bit irritable and short during the days of a full moon, not much different from the PMS moodiness a lot of girls get. Link came in 1960 and fought with von Wolfmann for a couple days until the wolfman put him in his place. After "taming" Link, he took him under his wing, taught him German as a first language, and sort of had a father-son relationship with him. He talked with Link during most of his imprisonment, and Link, after learning English from the Invisible Man, became a crude translator between the rest of the monsters. von Wolfmann called the Invisible Man "Unsichtbare", the German word for invisible, and Dr. Cockroach "Kakerlake", the German word for cockroach.
He died of old age in his sleep in 1965. Reverted back into a human when he died. His body was never sent back to Germany, not only because whatever family he had left couldn't be identified and found but because he was and still is regarded by the German government as a war criminal. His cell is completely sealed off and serves as his tomb, never to be opened again. Link was pretty devastated at his passing and Insecto sort of filled that void in his heart. He's forgotten most of the German by now but remembers some if something in German pops up like in someone else's conversation or in a movie/TV show.
(pronounced like Siberian), also known as Cy, an unfinished cyborg from the former USSR. She was in Area 5X from 1981-1985 and the second female monster in the facility's history.
Abilities and personality:
Her left arm was a power cannon that could shoot power beams when her wrist was fully bent downward and her fist was clenched. Her eyes lit up in the dark and could be a projector of her memories like a video. She was resistant to most physical pain and her longevity was expected to be longer than the average human's, maybe even longer than Dr C's. She couldn't be suffocated but she wasn't waterproof due to her cyborg-transformation being incomplete, and her body, like most electronics, would begin to shut down after half a minute of being submerged in water. If rescued within that time frame, she was drowsy and weak but eventually recovered. Ultimately, the only thing capable of completely destroying her was herself. She was brutally honest, didn't believe in flattery, told something like it was, and had to be trained in the art of discretion. Like, she wouldn't be afraid to slap a Karen across the face and tell her to shut up. But down to the bottom of it, she was sweet, gentle, and friendly. In cases of strong emotions, she absent-mindedly spoke more Russian than English, oftentimes forgetting that no one else understood her. She LOVED chocolate and wasn't expected to share, even if she got a giant bag from Costco.
She was born in October 1962 in Yekaterinburg [in modern-day Russia] and raised there. Her former name is V.P. Telegina. Her parents divorced when she was 2. She was raised by her dad and paternal grandparents, and her mom hardly had anything to do with her. At the age of 18, she, an aspiring engineering student, was kidnapped and partially transformed by her uncle, a scientist unofficially and secretly working for the Soviet government, to be not just a cyborg--a walking, talking weapon disguised as a human being--but the link and key to a weapon of mass destruction. He was going to use another subject but after having a fallout with her father--his brother and also a scientist, he decided to retaliate. Her father, trying to help her, was framed for assault and imprisoned. She was taken into custody by the government until her uncle could get her back and complete her.
Capture and imprisonment:
She was rescued and smuggled out of the country by USA spies within the following two days of her being held by the Soviet government. At this time, her transformation was only in progress and would be permanently halted. She was the only monster who chose and agreed to have her name changed and be locked up in Area 5X. Her "capture and imprisonment" were a coverup to keep her hidden from the Soviet government. However, she wasn't told that her fellow inmates were monsters when she brought to Area 5X, so she was definitely afraid when she met them but, after learning they weren't gonna kill her or anything, she came to love them and referred to them as her boys. She actually could've left the facility in 1992, shortly after the USSR collapsed. She was proud to be Russian and always would be. However, she didn't approve of needless violence and attacks against humanity (like what's been going on in Ukraine. She would've HATED Putin), especially since she was transformed against her own will for the sake of assaulting innocent people. She spoke only Russian when she arrived but learned a good amount of English from the Invisible Man and Dr. Cockroach as time went on. She and Link taught each other English and Russian swear words. She was only monster who didn't call Dr. C "Doc" (other than von Wolfmann); she had always called him "Doctor". She was present when the Invisible Man died in 1984. The two had bonded in a father-daughter relationship over the years as he kinda reminded her of her own father, so she was pretty upset. Throughout her "imprisonment", she put up a front of toughness sometimes, especially when she first arrived, but really felt overall vulnerable and often uncertain, sometimes afraid, of herself. She had quite a bit of pent up anger and depression about her transformation, who did it, some post-divorce childhood problems courtesy of her mom, etc., but she couldn't express or confide them well due to her poor English skills. She was never happy about being a cyborg. The only way to make her happy about it was to either revert her back to her fully human form or put her to good use.
She committed suicide in 1985 (in her cell after excusing herself from the common room) by shooting her head off when she learned via newspaper that her father, the only person who not only knew how to restore her to her original human body but was willing to do it, was executed [this was when Monger allowed the monsters to have copies of their formerly local newspapers] and that she would always be a cyborg, a means of death and destruction, forever. She was 22, the same age Susan was in the movie. This type of parallel pulled a lot of heartstrings for the rest of the monsters, especially since Link and Dr C briefly saw the aftermath of her suicide right before Monger sent them away to their cells. The two unnecessarily felt responsible to some extent for what happened and, when Susan came, Dr C vowed to never let that sort of tragedy happen again. Cy never shared what she read in the newspaper, and none of the monsters could read or understand Russian, so only Monger, via a Russian translator, knew why. Her suicide was the main reason Susan had that "Hang In There" poster in her cell in the movie. Another part of Area 5X has participated in a few different experimentations since the 1950s, like nuclear weaponry, aquamation (cremation with heated alkaline water instead of fire) and whatnot. Robosapien's body was used in cryonics testing shortly after her death and so far she's still intact and well-preserved to this day. Only Monger and a few long-time personnel in the Monster Containment Facility know. However, with the advancement of technology and modern science, some scientists in Area 5X have contemplated reviving her as a semi-artificial human, and it would be possible because she's a cyborg. It's a morbid, disturbing concept that a handful of people are uncomfortable with, but overall her future is unknown.
BONUS - A/U if Cy was still alive by the timeline of the movie
She chose to stay in the facility after collapse of the USSR in 1991, which the news totally blew her mind. Fast forward...she was a bit apathetic towards Susan's case at first, believing that her size was irreversible, and for that reason is the only monster who doesn't call Susan by her human name. It's either "Ginormica" or "Ginochka" (first 1 [or 2] syllable[s] of a name + "-ochka" is a Russian take on nicknames/terms of endearment for people). The only time she called her Susan was when the monsters were trapped in Gallaxhar's ship and urging her to leave. Nevertheless, Cy cares about her and is protective over her like the cool streetwise older kid mixed with a mama bear; their relationship isn't a besties one. She finally embraced herself as a cyborg because her being finally has a sense of good and purpose: saving the world. She wants the rest of her transformation completed in order to better help Team Monster. She was introduced to alcohol shortly after her release and LOVES hard liquor. She and Monger are the ultimate rivals in a drinking game. A couple of the monsters want a wifi hotspot to be one of her transformation features, but she has already said a big NO. She's been regarded as beautiful, like Susan, probably being featured on the cover of Vogue at least once. Russians hailed her as a hometown hero, and the Russian government tried to claim all the credit for saving the world.