|Other names:||Pissrock, Baby Kidney Stones, Sample H00128|
|Native zone:||Membrane layer|
|Residence:||Membrane layer, the Hospital, tote bag|
Little spiked kidney stones with childish behavior, almost always amused. They are made of 10% calcium oxalate, 10% calcium phosphate, 30% uric acid, 40% miscellaneous variable mineral compounds and 10% live, undifferentiated organic tissues. On the inside, they have microstructures in predictable patterns of supporting struts and hollow channels. Their organic tissues are sensitive to smell, taste and vibration. Their core is made of dense muscle-like cells with a pulse usually matching the rate of the human hearts. Their underside is softer and also the place where their circular mouth opening is located. The spikes around the mouth act as teeth, and the other spikes are capable of very limited articulation. Their diet consists of any and all animal materials, all non-animal sources of calcium, stone, concrete, steel, plastic and glass. Even without sustenance, their mass increases over time at a steady rate. The stones can form orifices on their surface at will, such as apparent visual receptors and vocalization pits. Despite their seemingly restricted locomotion, kidney stones can move smoothly on any surface, regardless of angle or material.
In Awful Hospital, a bunch of them were bothering Nobody Nose causing him to arrive at the Hospital for treatment. This treatment actually consisted of waiting until the stones grew bored of their juvenile behavior and leave on their own. Sadly, not being aware of them, Fern gave the nose a Ded-stone Fogger which killed them. This caused their mother to be enraged, breaking the wall and killing Nobody Nose. Upon hearing the noise, Green entered through the hole only to confront Kidney Stone Mother in combat. Fern succeeds in killing the giant kidney stone, leaving her young to mourn her. The little stones quickly return to their cheerful behavior and start feeding on their mother.
For whatever reason, one kidney stone came to Fern to follow her. She entered her tote bag to sleep and being carried around like an item in her inventory. She eventually befriends Ramblin' Evil Colorectal Polyp which comes to join Fern's inventory. The kidney stone can be used as a battle minion, having the ability to "agitate all enemy bladders" which deals 1 point of damage on each turn. This is achieved by generating regular kidney stones in the target's bladder. It's revealed for the first time that she's a girl when Willis talks to her.
- They are used by their mother to attack.
- Fern's companion kidney stone is level 25 and has 71HP.
- The PPP Association classifies them as threat category George.
- During the battle with Final Jayslob, Fern's kidney stone delivered the final blow by launching one of her crystalline thorns.