Prancer (1989)

Refusing to give up her belief in Santa Claus, a child, Jessica Riggs (Rebecca Harrell), discovers a hurt reindeer in the woods, which she believes to be Prancer. With the help of a sympathetic veterinarian (Abe Vigoda), Jessica takes care of the wounded creature. It's supposed to be a secret, but eventually a store Santa Claus (Michael Constantine), the girl's dad (Sam Elliott) and the entire town find out about Prancer, leading to big problems for Jessica and her family.