In 1957, Corning's Pyrex kitchenware designers devised a few new shape models to freshen things up a bit. These were, primarily, a set of four nesting mixing bowls, with new round casseroles in a handful of sizes following in 1958.
The mixing bowls differed from the original nesting set by the addition of diametrically-opposed flares in the rims which gracefully taper from the sides of the bowl, serving as a convenient grippable handle and a pour spout. Their designer was John Phillip Johnson.
As opposed to the older opalware round casseroles, the new casseroles were cylindrical, with straight, slightly tapered walls like the existing oval casseroles, but with narrower, tapered handles.
Each have design elements echoed in the "Family Flair" dinnerware bowls also introduced in 1957.
The naming of these new pieces as "Cinderella" likely had much to do with the popularity of the Cinderella story current at the time both in film and on Broadway. Corning marketers also hoped the underlying theme of a coveted glass object would have a subliminal effect on consumers.
The Cinderella branding would also be extended to over two dozen items, including promotional sets not necessarily of the "Cinderella" design, among them a Space Saver casserole set and a Hostess bowls-based chip & dip set.
Oval open bakers and divided casseroles were also grouped under the Cinderella moniker, although the oval casseroles were not.
As the popularity of Cinderella faded both in the media and in consumer minds, the name would be dropped from advertising, and references to the pieces in literature would become more generic. The term is all but absent from the 1964 retail catalog, only being seen used inconsistently on ancillary materials in the back of the booklet.
It appears, however, that the Disney version of Cinderella may have stuck in the minds of Pyrex marketers, as seen in the font in the literature for the 1968 Daisy collection.
The popularity of the fairy tale Cinderella notwithstanding, the Pyrex "Cinderella" shapes enjoyed consumer favor right up to the very last pattern collection released, Colonial Mist, in 1983.