Let's Be Happy is an updated remake of Jeannie (1941), one of the most likable British comedies of the 1940s. The premise is basically the same: A working girl inherits a fortune, goes on a fling, is rescued from a caddish seducer by a down-to-Earth salesman. In Jeannie, the girl uses her legacy to get out of Scotland and tour the continent; in Let's Be Happy, the girl (Vera Ellen) is an American who travels to Scotland to assume ownership of her family's castle. Since stars Vera Ellen and Tony Martin (as the salesman) were musical comedy performers, Let's Be Happy obliging becomes a musical comedy.
~ Hal Erickson, All Movie Guide