I think it’s the snakes who should be careful.
playing "Tom, Tom the Piper's Son" on his harmonica just in cast anyone forgets), but the focus for now is still on establishing the setting and its denizens as indelible parts of the story.
passed his entrance exam - it's a given Sebastian will, but Ciel needs a lot of painful help from him to skate by - he's given the rather ironic stage name of "Smile". As for Sebby his is as literal as Ciel's is not - "Black". Things superficially seem as normal as they get in this sort of life as Joker shows the newbies the lay of the land, but even more than usual with circuses Noah's Ark is riddles with mysteries. Snake is obviously a big one - Joker tells Sebastian and Ciel that most of the "first-stringers" are childhood friends, but Snake came along later. And it's his nest of vipers that acts as the barricade preventing access to the off-limit tents where the stars hang out.
William T. Spears, the imperious Shinigami working under the name "Suit". He's making no effort to hide his true nature and reacts quite openly when he sees Sebastian, but the others at the circus all take him for a joker and eccentric. His presence is yet another clue that something is going down at Noah's Ark, but not even Sebastian has any idea what that is. He has no sense of any of the missing children, but of course Ciel can't give up when he's on Victoria's secret orders. The idea of peeling back the layers of a circus to reveal the mysteries hiding beneath is unsettling in any circumstance, but in this mythology the possibilities positively boggle the mind.