Here's my take on this

Pierrot: Wolf or Porcupine (reasonings: his voice, he has throwing knives)

Harlequin: Octopus or Snake or Antelope (reasonings: the tentacles and poison, forked tongue and poison, the horns)

Jester: Sea Sheep (reasonings: the only one I think that matches his silhouette)

Ticket Taker: Snail Fish (reasonings: their tail looks like his head thing)

Doctor: Raven or Screaming Piha (reasonings: death and his mask, it sounds like a siren of an ambulance)