Iwata Asks, Kirby's Return to Dreamland producer Shigefumi Kawase revealed that three installments in the franchise were killed off mid-development, explaining "We spent 11 years ... making and abandoning these three games."
The three Kirby titles in questions would have been starkly different: One was a 2.5D four-player adventure title (sort of like Return to Dreamland, but with more depth), one was a fully-3D exploration-centric game and the other was an animated platformer with "pop-up visuals." They sound charming as all-get-out, which makes us all the more forlorn that they're dead as doornails. Goodnight, sweet princes. May flights of angels sing thee to thy rest.