In 2012, Brandon Cronenberg, son of David, released a movie called Antiviral about a niche product -- viruses and bacteria harvested from celebrities who become sick, in order to inject them into paying clients who want a "connection" with the famous.

What exactly was the rational behind that?

I mean, if people are willing to pay money for Gwyneth Paltrow's vagina eggs or Twitch streamer's bath water, I can only imagine the small fortune people would pay for a bacteria transplant from a famous person, even if it had no effect whatsoever(you can always craft a cleverly worded ad that suggests there are benefits but never actually states so as a fact).

It would have an effect though. That's a direct alteration to your gut microbiome. I guess, sure, fetishists are a thing. But I'm not sure it's a viable target market haha.

You could probably sterilise it so there's absolutely no live anything remaining and people would still buy it. But yes, it's probably a tough market :-P