Two on Top (1965)

A deckhand, Rolf Just Nilsen, is mistaken for pop singer Dickie Dons, also played by Rolf Just Nilsen, aboard the car ferry from Kiel to Oslo. The deckhand quickly settles into his new role and enjoys drinking champagne with the captain. However, things become more difficult as time goes on – not least because Dickie Dons turns out to be secretly married to his secretary.