Fred and Judy
When Gene Kelly injured his ankle, his replacement as Judy's co-star in 1948's Easter Parade was none other than...Fred Astaire. (Luckily for fans -- it brought Fred out of a self-imposed "retirement" from the screen.)  Judy's unique combination of ironic wit and naiveté serves her well as Hannah Brown, the homespun singer whom Don Hewes (Astaire) tries to make into a glamour girl a la his former partner, Nadine (Ann Miller).  Before the movie's over he comes to his senses, and falls for her besides, just as we do.  Fred and Judy make a remarkably pleasing team, making us sorry that this was their only on-screen pairing.