A man was left creeped out by an unusual yellow growth which appeared in the corner of his bathroom.
The unnamed homeowner, from Sydney, New South Wales in Australia, shared a photo of the bizarre abnormality on Facebook in the hope of getting some answers.
Posting in a Willoughby-based community group, he asked: "Does anyone have any idea what this is growing in the corner of my toilet?"
Others were mostly baffled, with one woman joking it looked like a "new lemon curd donut", while others compared it to a toilet duck and jellyfish.
Some commenters even likened it to the deadly fungus growths seen on the 'infected' in The Last of Us TV show and video games.
"It's the start of the apocalypse," one woman wrote.
Another person said the bathroom needed "a good clean and regular airing".
The growth has since been identified as a fungi known as a Flower Pot Parasol.
It is commonly found in flower pots and greenhouses but an extreme rarity to have one inside a bathroom.
Dr Tom May, Principle Research Scientist of Mycology at the Royal Botanic Gardens Victoria, told Yahoo News Australia: "It's a sure sign that there’s wet wood behind the panelling."
He said such fungi will feed on decaying matter, meaning damp has set in inside the man's walls.
It can spread like mould, and potentially causes respiratory related issues for those living in close proximity.
“You definitely don’t want a mushroom inside your house releasing spores," the expert added.
It comes as new types of fungi could pose an alarming threat to humans in the years to come as scientists fear a Last of Us-style scourge.
Fungi could evolve more resilient and vicious against humanity due to climate change, which drives the temperatures higher, as well as due to the advancement of medicine.
Patients become more susceptible to fungal infections and fungi more resilient, making antifungal drugs less efficacious, a medical professor has said, describing how a dystopian scene such as those in the Last of Us could one day become reality.
The HBO show, which is based on a video game, features zombies infected with a real parasitic fungus called Ophiocordyceps unilateralis that can take over the brains and bodies of insects, turning them into real-life zombies.
