While significantly less intense than Osmosis Jones, the series has its fair share of bodily beasties and moments that'll chill you to the bone.
- The entire series can be terrifying given the circumstances, Osmosis and Drix are now settled within a 13-year-old boy. Frank's health and situation with disease was bad enough; now imagine those things affecting a teenager…
- In the first episode, Ozzy and Drix are accidentally transferred to Hector via a mosquito bite. What comes with them? Scarlet Fever, meaning Frank's enormously fat body (since he's noticeably fatter since the movie) is literally killing him. Especially since we don't know if all the Scarlet Fever came in the mosquito or if Frank still has it.
- Frank either relapsed from the movie and is in even worse health, or it's an alternate continuity. Either way he's in notably terrible shape (Ozzy points out everyone is working overtime lately) Drix wonders why they even bother trying to keep him clean if Frank is just going to keep up with his bad habits. Though given Frank does make a cameo a few times, it's at least assumed he can at least leave the house.
- The villains are especially terrifying if you have any sort of medical knowledge. Case in point the Ernst Blofeld Expy Strepfinger and Scarlet Fever in the pilot. Two different strands of streptococcus who could’ve done serious damage to Hector's respiratory system.
- Just the Queen Louse in "A Lousy Haircut" with her and the eggs lain coming more across like Xenomorphs can send a real chill down your spine. Especially with how close she comes to killing Ozzy.
- "Where There's Smoke" has the villain Nick O’Teen and his chemical-based henchmen almost succeed at completely taking over Hector through making him addicted to cigarettes. Nick is remarkably similar to Thrax from The Movie, only difference being his red glowing fingers can hypnotize other Cells turning them into nicotine-craving zombies. Not helping that Nick and his gang aren't simple viruses or bacteria; but carcinogens and chemicals, so defeating them takes more ingenuity. Like, for example the brutal deaths of Butane, Carbon Monoxide and Tar being burnt alive and exploding via a nerve cell overloading. Ozzy and Drix are completely helpless to stop Nick, and the only reason he doesn’t succeed is Hector's own willpower; he remembers Christine's disapproval of him smoking just one cigarette.
- The Dream Factory has Ozzy and Drix deal with a literal nightmare in Hector's subconcious affecting his sleep because he saw a scary movie. At one point Hector is so disoriented he almost gets run over by a truck!
- The episode "Ozzy Jr." borderlines on pure Squick since it's about Ozzy believing he's pregnant, but once it’s revealed WHAT he's carrying, things get a lot scarier. Strepfinger infects Ozzy with a listeria
bacteria that he plans to grow and infect every single cell in Hector's body until they all die. - "Lights Out" is all about Hector suffering a concussion because he decided to skateboard without a helmet. Throughout the episode Hector displays very real symptoms of a concussion like dizziness and increased drowsiness. The worst part of it is that Ozzy and Drix are the only ones aware of what happened because the impact caused a mass of short-term memory loss to every other Cell in Hector. Drix states that if they can’t kickstart Hector's brain? He might fall asleep and die! Fortunately, Hector's best friend Travis finds him in time.
- "The Conqueror Worm" has Hector eat undercooked chorizo and get a pair of Trichinella spiralis or flatworms. In addition to the episode essentially being a Whole-Plot Reference to Jaws to amp up the threat these worms pose? At one point Ozzy literally comes face to face with one, and it does like a Xenomorph revealing a second mouth! Fortunately, it dies then and there, unfortunately that was just the male, the female survived and was pregnant. And the female? She was even SMARTER than the male… not to mention how she was killed…
- "A Growing Cell" has a cholesterol germ named Stickety Lipid kidnap the children of fat cells due to Hector's increased consumption of fast food and weight gain in an attempt to clog an artery and induce a heart attack.
- "A Cold Day in Hector" is probably the closest he's come to actually dying. Hector gets into a small avalanche while snowboarding with his friend Travis, rips his snowsuit and gets a bad case of hypothermia and the denizens of Hector have to deal with Cryo; an Anthropomorphic Personification of the frigid cold trying to drop his body temperature. Unlike other villains such as the Lead Gang and Nick O'Teen's crew, Cryo isn’t a chemical or substance; she isn't even a virus or germ. She is the living embodiment of the cold and can't be dealt with by conventional means. What's worse is that Drix is the only one unaffected by the cold. At one point, Ozzy suffers from the frigid temperature in a state of delirium. Hector is on the very brink of death with him only being saved by pure luck.
- "Triumph of the Supplements" gives us the Lead Gang, living heavy metals Hector snorted into his system after accidentally inhaling lead paint he and his father were removing from a shed. The effects of lead poisoning Hector endures are on full display; the boy is barely able to function. What's worse is we actually see the Lead Gang EATING the lining of Hector's stomach AND his nerves! Not only are Ozzy and Drix's weapons useless against these villains, The Supplements aren't enough to destroy them. The Lead Gang ultimately has to be subdued and literally FLUSHED out of Hector via his bladder.
- The penultimate episode "When Nature Calls" has Hector deal with his appendix about to rupture in the middle of the woods during a river rafting trip. Billy Bob Bile, a seedy hillbilly germ had it turned into a hotel detouring from the small and large intestines, causing an influx of viruses and bacteria to clog the organ up. Had it burst? Every single germ and virus packed butt-to-gut in there would've flooded the bloodstream and made Hector seriously ill or even killed him! Thankfully, one of Hector's friends was quickly able to determine what was going on and he and the other friends were able to get Hector to the hospital in time.
