In 1929, the musical film was still feeling its way, trying to learn what works and what doesn't. Sunny Side Up is one of the best of the early musicals, a refreshing and engaging piece of fluff that still holds interest today. Although the story is essentially a variation on the Cinderella story, the script has a number of good lines and more than holds the viewer's interest. Director David Butler turns in a fine job, overcoming many of the problems of the early talking picture cameras to give the film a more fluid, mobile feeling than most of its contemporaries. The opening is especially good, with the camera moving in and out of the urban set, and Butler also handles the story's important class conflict well. Janet Gaynor is adorable as Molly, bringing a nice combination of innocence and ambition to the role, and carrying the picture despite a distinctive voice or special dancing ability. Charles Farrell is not as skilled as Gaynor, but they work well together as a team. The DeSylva-Brown-Henderson score is superior, with "If I Had a Talking Picture of You" and especially "Aren't We All" exceptional. The film's undeniable highlight is the bizarre but fascinating "Turn On the Heat," a surprisingly upfront celebration of sex that is filled with energetic, uninhibited writhing and slithering; it's the type of one-of-a-king moment that must must be seen to be fully appreciated. Butler would go on to direct many musicals, including several with Shirley Temple and Doris Day.