List of New Super Mario Bros. Wii pre-release and unused content

Beta Elements from the game New Super Mario Bros. Wii.

Propeller Mushroom
The orange Propeller Mushroom was originally a Propeller Suit, a red letter "P"-like suit with a propeller at its top. It's unknown why the makers changed it into a Mushroom.

Level Designs
Many of the platforms were redesigned as many of them were orginally plain in color. There are also differences in mechanics of some of the platforms. There was earlier going to be platforms moving on their own, close by growing and shrinking pipes, but those platforms can now be controlled by players doing something specific.

Fire Toads
Originally the fire Toads had caps which had their respective colors reversed with white spots on them. In the latest screens from the games, the Toads instead have red spots on their caps.

HUD during gameplay
During the early screenshots of the game, the HUD originally appeared transparent during gameplay; additionally, the text appeared very different, with only generic font; possibly as a placeholder. Recent screenshots of the final build show that the HUD is now solid, certain icons were updated or brightened up, and along with the trademark Mario text. Notably, the life box was sized down, while the score and timer stretched out slightly.

Also, when a Yoshi is ridden, a Music Note appears on the upper-right side of the screen. This may have been deleted because that people may intend that the note stands there for no reason

Red Yoshi
Earlier at announce, Nintendo confirmed that a Red Yoshi is ridable (even an artwork of it has been made, saying that it would stay so). However, after a newer trailer, Red Yoshis haven't seen ever again in this game, but instead, Pink Yoshis has been added (the artwork for the Red Yoshi has changed too to match the current change). It may be possible that the Pink Yoshi replaced the Red one.