Opportune Odors Horseradish Factory is, as its name implies, a horseradish factory located along Lousy Lane, and is responsible for causing the smell of horseradish in the surrounding area. It produced horseradish as an antidote to the Medusoid Mycelium.
Kit Snicket, when writing to Gregor Anwhistle, mentions the factory is producing horseradish to combat the possible weapon of the Medusoid Mycelium, but she does not believe it will be enough; she begs him to stop production, and he eventually perishes in a fire, though the medusoid survives.
- The Reptile Room (mentioned)
- The Grim Grotto (mentioned)
- The Penultimate Peril (mentioned)
- The End (mentioned)
- Lemony Snicket: The Unauthorized Autobiography (mentioned)
- Lemony Snicket's A Series of Unfortunate Events (video game) (PC version only)