Don't forget Bow as well at the end PM:TTYD, Fawful and Geno in the Mario bros games.
Mario's mission.
After attempting to save Princess Toadstool from Bowser, Mario gets flung from Bowser's Castle and crash-lands in his house. After venturing back to Bowser's Castle, Mario finds the giant sword Exor lodged in the roof of it. Learning that his world is being invaded by the Smithy Gang, Mario is forced to retreat to his house after Exor destroys the only bridge to Bowser's Keep.
1. Mario was asked by others to save their world, get Bowser's keep back, save the Peach and help Mallow
2. In order to get Bowser's keep back they had to beat smithy.
Geno's mission.
An otherworldly traveler sent by a higher authority, whose real name is

♪!?, comes to Mario's world from Star Road to find the seven Star Pieces. Borrowing the form of Gaz's doll, Geno, a beam of light radiates from it bringing it to life, and he sets off searching for the Star Pieces. Since his name is hard to pronounce, he asks Mario and Mallow to call him "Geno", after the doll.[4] [5]
Encountering Mario and Mallow during his battle with Bowyer, Geno gladly accepts their help in battle. Defeating Bowyer, Geno explains to Mario and Mallow about his mission to find the Star Pieces and repair Star Road. Geno decides to travel with them to find the Star Pieces. Throughout the game, Geno offers advice to the party as a mystical sage-type figure. After destroying Smithy and reclaiming all seven Star Pieces, again a beam of light radiates from Geno, rendering the doll lifeless, and the otherworldly traveler bids farewell to his allies in order to repair Star Road.
1. HAd to get the star pieces back
2. Had to beat Smithy for the last piece.
So all 5 characters are the main characters.