Poop - curious

This is just a question out of curiosity. I have noticed that if either Pip or Chomsky goes to use the kitty litter box, then the other one will run to check it out as soon as they can hear the litter being scratched. Then more often than not the second to arrive will decide that they have to use the box too.

Why do they do this? It seems so funny to me!!

You can tell a lot about the poop of your roommate , especially what they have just eaten. That is why, for example, dogs sniff each others' tails/butts.
Now, if your cat(s) decide to EAT the others' poop, I would be concerned.

Mine tend to use their box within about half an hour of each other. Sabbath always attempts to clean up Felix's mess also as Felix isn't capable (he's missinf a front leg).

My cats also tend to want to do their poo whenever I'm about to sit and eat something or am very busy. It's like spite haha.