That last one's definitely amusing.
I've seen a player leaving 9 expansions in the middle locked, and unlocking expansions around it, until their city eventually became this square bold border around the locked slots in the middle. That was the weirdest one I've seen, though it was on another server so I'll avoid chatting about that one.
I do like how one can basically make an art piece if they arrange the expansions somehow and place the right buildings there. But I always make my cities efficient rather than 'pretty', I don't think I can get myself to mess up my expansion unlocking and building preference just for some final pretty outcome.