As for Bowser Jr. and Captain Toad, Bowser Jr.'s debut in
Super Mario Sunshine would give him enough moveset potential on its own to make him worthy of inclusion in
Smash, though it definitely helps that he was the primary antagonist in that game and played a major role (Bowser only showed up at the very end, with the game barely hinting at his presence before he showed up). In fact, it was specifically the
Sunshine portrayal of Bowser Jr. that
I supported for Super Smash Bros. Brawl. Captain Toad, on the other hand, really wasn’t all that important in
Super Mario Galaxy (though he may or may not be the same Toad who's been a major character in games like
Super Mario Bros. 2 (U.S.) and
Wario’s Woods, who is certainly important enough for
Smash on those grounds). Really, it’s
Super Mario 3D World and
Captain Toad: Treasure Trackers that elevate the Captain Toad identity to the level of prominence required for representation in
Smash.