Four Jacks and a Jill is a 1942 musical comedy film starring Ray Bolger, Anne Shirley, June Havoc and Desi Arnaz.
Opal, who is dating a gangster called Noodle, quits the band, which then loses its nightclub job.
Nina claims she once was a singer who entertained European royalty, King Stephen, and gets the band hired by a club owner called Hoople who believes her tale that the King himself will come see them perform.
But, by coincidence, taxi driver Steve Sarto, who is trying to woo Opal, is a dead ringer for the King.
He comes to the club pretending to be his majesty, but Noodle wants to flatten him for paying too much attention to Opal, and then confusion reigns when the actual King shows up.