So, it has been about 4 weeks since he broke up with me. I went to our apartment to move out and found a list entitled "Things about you that make me smile". I assumed it was something old he wrote to me a while ago, but after reading it, I realized it was not meant for me. It looks and sounds just like something he wrote to me a while ago. The things on the list could be things describing me, except for some small differences which is why I know the list was not meant for me. Some of the things are exactly what he wrote to me before.

Also, he hasn't done anything to the apartment besides make it a huge mess. It's really sad because it smells horribly in there. He hasn't taken down the pictures of us that are on the fridge or put anything else away.

Is it me, or is this odd behavior?

He is your ex and so I wouldn't even worry about it.
It doesn't really sound like he has somebody else with the little you have to go on.
It could just be more of a wish list than directed to any specific girl.
If he is inviting girls or a girl over I would think he would want to clean it up and take your pics down to try and impress her. Sounds more like he is in depression of a break up

Don't over think this, and do not start questioning yourself and do not try and analyze what he is up, it will only uspet and annoy you. Throw away that list and keep moving on. You don't care what he does now, so why think about this.