A Little Romance (1979)

Intellectually precocious teenager Lauren King (Diane Lane) lives in Paris with her somewhat ditzy mother (Sally Kellerman). On a movie set, she strikes up a friendship with teenage film buff Daniel Michon (Thelonious Bernard). After Lauren's mother forbids her to date the outspoken Daniel, the young lovebirds team up with eccentric pickpocket Julius (Laurence Olivier) to run away to Venice, where, according to legend, a couple who kiss under the Bridge of Sighs will stay together forever.