1. Calvin- A dear friend of Petey's, abandoned at the mental hospital
  2. Esteban (Human)- A kind Mexican man who loved Petey, feeding him chocolate and teaching him
  3. The Mice (Esteban, Blackie, Cloud, sally,william, the pups)- Mice who eat Petey's food scraps and lick him lovingly
  4. Joe- A man who entered Petey's and Calvin's lives when he saved Calvin during an accident and celebrated the boys' first Christmas
  5. Cassie- A nurse at the Mens' Ward, as well as Petey's crush. She also has a daughter and a long distance husband.
  6. Will- A kindly old man who retired to work at the Mens' Ward and helped Petey and Calvin to come out of their self-imposed seclusion
  7. Sissy- A polite young lady who works at Bozeman Nursing Home and takes a special interest in Petey and his life story
  8. Trevor- A young boy determined to make Petey's last months as enjoyable as he can
  9. Sadie- An older woman who plays receptionist for Calvin's group home.
  10. Shawna- A young girl who takes an interest in Petey after Trevor runs his mouth at her
    • The Mice
    • Esteban
    • Joe
    • Calvin
    • Cassie
    • Owen