It’s actually a street phenomenon that may have been going on for many decades (?). The vent pipes that get painted are common to many buildings here, and have been around for ever. Certainly, numerous artists get inspired to put their stamp on the familiar prank. Here’s some that someone took a particularly good amount of time with (considering).

It’s nice that the city still has some magic in it, and that it all hasn’t moved to Oakland, chased away by the $1000 strollers.