I do that sometimes. Or I'll imagine what all their skin
   sensations feel like simultaneously. Or hearing all the things
   they hear at the same time.

   To really mess with my imagination, I'll even try to imagine all
   their perspectives and everything they see with their eyes at
   once, then go Beastmaster and imagine it for the animals.

   It's not something I do everyday or often but once in a while, I
   go, "I wonder..." and let my imagination fill up with lots of
   people from inside their perspective simultaneously overlapping

   I think it's a good mental exercise from time to time.