On The Riviera synopsis
While performing in the French Riviera, entertainer Jack Martin (Danny Kaye) finds he can do an uncanny impersonation of wealthy businessman Henri Duran (also Kaye), so much so that no one can tell the difference between the two. When a pressing business engagement requires Duran's presence, he hires Martin to take his place at a party Duran is supposed to be hosting. It turns out the plan works -- too well. Soon, Martin finds himself beset by Duran's wife, as well as his many mistresses.