Most of the characters in Susan E. Hinton's novel, That Was Then, This Is Now, receive some sort of symbolic treatment. Mike Chambers refers to himself as "making like Sir Galahad"--a white knight coming to the rescue of Connie, the black girl hounded by white teens. "M&M" is named after the candy he constantly eats, and the candy itself is symbolic of the boy's addictive personality. Charlie symbolizes the would-be hero: He is drafted but cannot serve militarily because of his past arrest record; the police respect him for the way he runs his business; and he comes to the rescue of Bryon and Mark, saving their lives at the cost of his own. Ponyboy Curtis symbolizes the intelligent gang member: He is introspective, brainy and successful at school; he is smart enough to avoid Angela Shepard and eventually hook up with Cathy Carlson; and he has a reputation as a strong fighter in spite of his small size. Dirty Dave symbolizes the dark side of bar life--an outsider, a bad loser and a murderer. Mrs. Douglas is symbolic of the Good Samaritan: She picks up every stray cat available; she takes in Mark as a foster son; and she convinces the boys to be friendly with Mike Chambers. When Bryon turns Mark over to the police, she tells him that "you'll just have to make him understand that it was wrong and that what you did was for his own good."
Focus on the character descriptions and how they relate to the personalities of the animals involved. Mark as a lion--generally docile in a comfortable setting but a fierce hunter and dangerous when threatened. Bryon as a St. Bernard--trusting, loving, idealistic. But with that in mind, what kind of animal could you compare Bryon to at the ending since he isn't those things anymore?