Why is Denny shocked when he meets the little boy?

Denny's shock upon meeting the little boy is rooted in the deep emotional and philosophical themes presented in "The Art of Racing in the Rain." Throughout the story, Enzo, Denny's dog, believes that he will be reincarnated as a human. When Denny meets the boy, the realization that Enzo's belief might somehow manifest—a connection between Enzo and the boy—catches him off guard. This symbolizes Denny's inner turmoil and the intertwining of life, love, and loss, all viewed through Enzo's unique perspective.

This moment emphasizes the bond between Denny and Enzo while also touching on the themes of identity and reincarnation that are prevalent throughout the narrative. It poignantly illustrates how the story combines elements of fantasy with emotional truth, allowing readers to reflect on the profound connections between beings.