Who is Wocket from Mick Harte Was Here and what is their importance?

Wocket is the basset hound that Phoebe's parents got for herself and Mick. The dog ate one of Phoebe's Barbie's soon after the family got the dog, so Phoebe was never really close to Wocket. Wocket, however, was Mick's best friend. When Wocket had to be put to sleep because of cancer, Mick stayed with her until she was gone. After her death, Mick would talk to the pictures of Wocket that he had tucked around the edges of the mirror on his dresser. Phoebe is comforted by a dream that she has in which Wocket is laughing in heaven.