I’m assuming you mean the cult of Instragram, which I have no intention of joining!
Seriously though… I hunted around a bit to find the story behind these messages. This is a street art project designed to cheer up London’s notoriously grumpy commuters and get people talking about emotions. He’s something of a minor celebrity and appeared in local papers / TV. However, I’ve changed the link in the story to one that provides more backstory.