The Frirus consists of tiny robotic germs that Robotnik sprinkled into some deep fried potatoes. He then sold the potatoes as French Fries at a phony fast food restaurant called McRobos, for the sole purpose of making the Freedom Fighters deathly ill, as their Auntie Bodies were not strong enough to fight this disease.
All of the Freedom Fighters except Sonic the Hedgehog ate the tainted food, forcing Sonic to shrink himself to microscopic size and enter Rotor's body to fight the Frirus himself. His unselfish actions against the Frirus's three components gave Rotor's Auntie-Bodies the courage to fight back, which they then communicated to the Auntie-Bodies of the other Freedom Fighters by means of a single-celled, cellular phone. The Frirus was defeated, and the Freedom Fighters recovered. (StH: #33)
The French Frirus actually consists of three components:
- Paris-Site: The leader of the French Frirus is a frog-like, beret-wearing parasite named Paris-Site, who prefers not to do the dirty work himself. He is content to let his henchmen do the dirty work, softening up the opponents until he can dispatch them with one hit form his "Microbe-Bar" crowbar. Before he could do so to Sonic, Rotor's Auntie-Bodie swiped the bar and killed Paris-Site with one swing. The Paris-Sites in the other Freedom Fighters were dispatched by their respective Auntie-Bodies, whose confidence and courage were restored.
- Fever: A living flame that serves as one of Paris-Site's henchmen. He keeps the Freedom Fighters sick by raising their body temperature, letting his boss take over. Physical contact is nigh impossible without burning oneself. Without his boss, however, Fever becomes a coward. Sonic managed to run around Fever, creating a vortex that removed the oxygen from Fever and extinguished him.
- The Foreign Lesions: Sores that line the membrane walls serving as Paris-Site's bodyguards. When an intruder comes across, they burst, spewing disgusting glop all over the intruder. Fortunately, Sonic destroyed this gross menace with one Sonic Spinball.
- The name French Frirus is derived from the names french fries and virus.
- Similarly, the name Paris-Site is derived from Paris (the capital of France) and parasite. (Paris-Site's beret is a traditionally French item of clothing.) The Foreign Lesions are named after the French Foreign Legion and lesion, which is a wound or a localized abnormal bodily change.