I have an outline of a story for ya!
Giana and Maria are happily playing in their world (Kicking some monster butt etc..) when Mario comes in and flattens Maria..
Giana being the smarter sister exchanges a few words with Mario (who screams about nintendo being better etc).. mario then proceeds to attack Giana in her own backyard!!
Sensing defeat Giana runs away and Mario stands smug in his new world..
Later that day Giana returns with our hero... Turrican
Who proceeds to unleash a bloody fury on 'ol Mario himself.. and recaptures Giana's home..
How about that?