Hollywood or Bust (1956) on Netflix

Malcolm Smith, a star-struck movie fan known for his lucky feelings, wins a new convertible in a theater raffle, but his ownership is challenged by compulsive gambler Steve Wiley, who hopes his forged winning ticket will help him pay off his bookie. After Steve regales a lovesick Malcolm with concocted stories about his supposed next-door neighbor, sultry actress Anita Ekberg, they agree to share the car on a cross-country trip to Tinseltown. Steve is prevented from abandoning his traveling companion on several occasions by the latter's pet dog, a huge and voracious Great Dane named Mr. Bascomb. They bond by sharing various adventures in New Jersey, Chicago, Oklahoma, and New Mexico. By the time they get to Las Vegas, where they meet the real Anita Ekberg and test Malcom's luck with craps, they have acquired a third member of their group, Terry Roberts, an aspiring dancer, who becomes romantically involved with Steve.