Why didn't they just simply put Red Toad to be apart of the cast (With Blue Toad still being there)? Well in Super Mario Bros. 2 for the NES, Toad's color was blue!
Color variance seems to be a more likely answer: 3/4 of the characters would be red and Luigi would be green, having Luigi stand out too much. However, making Toad blue and making Mario's Cat Suit yellow gives the characters better color variance.
The concept art containing two of every character seems like a way to show their cat suits alongside their regular outfits. Then came the reveal of the Double Cherries...
Though in actual gameplay, doubles always wear the same suit as each other.
During the intro, Luigi jumps into the pipe last. Not only that, before he jumps into the pipe, you can clearly see him cower for a bit before slapping himself in the face and following the other characters. Nintendo is clearly acknowledging his Lovable Coward personality in a game with very little dialog here.
In both Mario 3D titles, Bowser appears to be completely defeated twice before you finally finish him for good the third time ( once in the second-to-last castle, twice in the last... the world 1 defeat is fake in the first game and flings him away in the second). In the new one, this can be explained by Double Cherries, but since it's three both times, it might be intentional: Bowser has three lives in each game and doesn't stock on one-ups. One thing holding this theory back though is that each player starts with 5 lives in these games, instead of the classic 3 from the original Super Mario Bros.
The two Luigis in Luigi Bros. could probably be explained by the Double Cherries alone note although the playable character's doubles all move in unison the Meowser clones were shown to be capable of independent movement but it also brings to mind the existence of two Luigis in Super Luigi Galaxy.
Why do you always start in Super form after losing a life? In Super Mario Bros. 2, when you lost a life, you start again with two hearts, Super and small form.
This one is subtle, in SMB 2, you start with two hearts and can earn up to five hearts. How is this possible in 3D World? For example: In Snowball Park, you can have up to five hearts by: (Ice Skate, Propeller Block, Tanooki Suit / Cat Suit / Fire Flower / Boomerang Flower, Super Form, and Small Form), thus giving you five chances to live.
The level Super Galaxy doesn't give you any powerups. This makes sense, since it's based on Super Mario Galaxy, which, using a different damage system, doesn't have any Super Mushrooms.
Rosalina loses her Spin Attack when she gains a power up. It sounds like this was purely to balance her out else she would be a Game Breaker. Not quite. Remember when Mario had the spin attack back in Galaxy 1& 2? All of the power ups in those games either altered or disabled his Spin Attack with their unique functions that required use of shaking the Wiimote except for the Rainbow Star. Naturally, her Spin Attack would be disabled if she used any of the power ups because they all had unique functions that required the dash/attack button (barring the Super Mushroom, Double Cherries, and the Super Star of course).
Some gamers have expressed surprised that Mario's Cat suit is yellow. In the cat fancy, yellow cats are classified as red.
Peach's Fire Flower dress is a callback to her attire in the original Super Mario Bros. In that game, Bowser could only be defeated directly by Fire Flowers... Looks like Peach was planning to spring herself, Mario just showed up faster!
The track that plays on the Great Tower of Bowser Land, the final main story level, is basically a remixed and more intense rendition of the track that plays before boss battles. And fittingly enough, it plays right before you reach the Final Boss.
Why is Rosalina's cat suit black? Simple: Black cats are closely associated in folklore with witches. Now, Rosalina is not a witch by any means, but she's the most magical character in the Mario series, hence the black cat suit for her. One of the Toads in Galaxy even thought she was a witch when he first saw her!
There's a goomba mask item that you can acquire several times throughout the game. However, since you always acquire the item by defeating a goomba, there's the notion that the item is not a mask, but actually the decapitated head of the goomba. And your character wears it over his or her body.note Jossed by the developers. They're supposed to be Papier Mâché masks. Then again, that doesn't stop one from thinking that it really is the head of a real Goomba, especially how realistic they look.