Of course Harry’s Tulpa is Ronald McDonald, the Burger King is a good memory. The trope of the scary clown (the Joker, Pennywise, Killer Klowns From Outer Space, Gacy) is well established enough in popular culture to have its own phobia. Indeed the Phantom Clown is an established urban myth, along with the slender man.
And remember all the way back in Storm From the advert “No children’s parties”, Harry obviously didn’t want to be near any clowns.