Maybe not that obscure, but the GBA Jazz Jackrabbit was meant to be the start of a new series for the system, and future games would eventually feature prequels (just like Star Wars did) to tie the new story with the old one. In hindsight, you can see how wishful thinking that was, and it's kind of silly how pretty much everyone involved with the project got sort of angry at how poorly the game fared, and JJ was deemed unprofitable as a franchise.

Some tie-ins explained by the developers involved Jazz divorcing Eva and as such losing any ruling power on Carrotus, and Dark Shell being as loosely related to Devan as Dark Helmet was to Lone Starr in Spaceballs (A+ originality)