There Were.....
....A lot of Corning pattern knock-offs back in the day. Most were for "go-alongs" like salt and pepper shakers, paper napkin holders and the like. One company that did a lot of this was Gemco, which had go-alongs for many Corning Ware and Corelle patterns. The companies specializing in this kind of thing always changed the pattern a little bit, changed enough to avoid accusations of outright copying, but close enough that many consumers really didn't realize they weren't the genuine thing.
"Spice 'O Life" was one of the most plagiarized patterns ever, with unauthorized variations of it seen on canisters, non-Corning cookware, paper plates, kitchen plastics like trashcans, you name it. K Mart seemed to carry imitation "Spice 'O Life" everything.
I never understood why Corning didn't do more to stop the copying. Instead, they actually partnered with Gemco on some authorized go-alongs, with the exact Corning patterns used instead of knock-offs.