Back in the good old days of home microcomputing, the only way to play some Super Mario Bros was on a console. Then in 1987, Time Warp Productions created Great Giana Sisters...
This blatant Bros clone pissed Nintendo off no end, and they promptly cease 'n' desisted the game off the shelves, only to have it pop up again as freeware in multiple unofficial ports for Linux, Windows, GBA homebrew, and many others.
By some freak twist of licensing and fair use alchemy, dtp entertainment seem to have acquired the rights to produce a proper, for-actual-money sequel to the game that will appear on the Nintendo DS. Presumably the Sisters adventures are just dissimilar enough to any subsequent Mario Bros outings to avoid Nintendo's ire, or maybe Ninty just don't care anymore and have instead been seized by some pro-feminist sentiment. Either way, Giana Sisters DS it is...
Famed Mario Rip-off Giana Sisters Coming to DS [Shacknews]