If you break open the B-K Game Paks that had the Ice Key and 2 other SnS eggs in the original Banjo-Tooie, these have shinier eggs in them now, but they don't have a ? on them. When one of these eggs are collected it says Stop 'N' Swop II.
Would this have something to do with B-K or NaB? Maybe Banjo-Threeie?