What song insinuates itself into all your playlists and why do you think it's there?

I never actually counted but thanks to your question I know now. Currently I am enjoying music on 45 playlists and there is zero songs overlapping, with a small exception of “temporary” playlist — where songs are awaiting being sorted and this one is generally a “beautiful mess”.

There might be like 5 songs that occupy different playlists but they are in different versions, covers, unplugged/concert versions or redefining remixes.