The Horse in the Gray Flannel Suit (1968)

Fred Bolton (Dean Jones) is an advertising man facing pressure from both his boss, Tom Dugan (Fred Clark), and his daughter, Helen (Ellen Janov). He needs to satisfy Dugan with a great promotional campaign for the stomach remedy Aspercel, while also making good on his shy daughter's deep longing for a horse. Bolton convinces his boss to buy a horse and dubs it Aspercel, with the hopes it will become a champion, bringing attention to the product and, ultimately, saving Bolton's job.