I quite often leave small piles of things on the bottom step of the stairs waiting to go upstairs. I also leave things on the post at the top of the stairs that need to go down.

I think this is normal behaviour.

Mattgreen, however, seems not to notice these things, and happily trots up and down the stairs without ever moving any of the items to their correct floor.

I find this infuriating.

Recently, as he stepped over piles of papers and toys waiting to go upstairs, I challenged him about it.

Later that day, Mattgreen noticed the copy of Mr Muddle that has been lying around on the post at the top of the stairs for days. Unlike the other items on the post, Mr Muddle didn't need to come downstairs; it had simply been dumped there. Nevertheless, Mattgreen brought it downstairs as a matter of principle.

While tidying up, I noticed Mr Muddle was downstairs when it should've been upstairs, so I put it on the bottom step. Later, I noticed Matt had moved it back up onto the post. I challenged him about his behaviour.

Apparently, Mr Muddle has become caught in an infinite space-time loop.