This would legitimately be the greatest prank anyone could ever possibly pull. It wouldn't even have to be 8 billion, just enough for everyone they could possibly interact with for a few days after landing. And they'd all have to really commit to the bit. I think this is the one thing that can truly unify us as a species.
It'd be even easier to do because astronauts usually have health checkups and quarantine after returning home. Most people would just need to wear hazmat suits.
That reminds me of the scientists who were in a "Moon Mission" Simulation in a remote area and completely cut from all society, going in before the pandemic and coming out of isolation in the hight of Corona and social distancing and stay at home orders.
I bet they wished it was a prank with ape costumes.