[jarel]

But how do you clean the cleaning brushes?

[Theriac25]

By making custom tooth-brush cleaning brush cleaning brushes that are tailored to each tooth-brush cleaning brush they produce?

[hamburglar]

At each iteration, the shape changes slightly, until eventually, the design stabilizes to a device that looks suspiciously like a turtle.

[jessaustin]

So you hypothesize that there exists a fixpoint for the cleaner function?