These are beta elements for Mario Kart 3DS.
In early development and Demos, the Poison Mushroom was depicted (which could not actually be retrieved in the demo version itself) as an item. It was confirmed that the Poison Mushroom would function similarly to the Mini Mushroom, making it obviously replaced by the Mini Mushroom instead.
The Burning Shell was supposed to be an Item, opposite to the Ice Shell. Being an opposite to the Ice Shell, it is assumed that it would burn players of course, but maybe leaving a trail of fire, or being more durable, etc. However, there's no information if there was going to appear a Triple Burning Shell but it was expected. It is also said that it was going to appear instead of Ice Shells, meaning they maybe have been replaced by them.
- Wingless Blue Spiny Shell
As seen in some unused files of the game, Noki, Big Bob-omb, Baby Donkey Kong and Giga Lakitu were going to be playable characters, but: Noki was replaced by Lakitu, Big Bob-omb was replaced by R.O.B, and Baby DK was replaced by Shy Guy. Giga Lakitu however, got scrapped from the game for unknown reasons and got replaced by Honey Queen, but he still appears in the game as the boss of Level 7 in mission mode, as well as Big Bob-omb appearing as a boss in Level 5.
There's also another folder containing the name "teresa" (Boo in Japanese) as well as a file called "teresa_icn" (however, the file doesn't show anything) maybe revealing that Boo was going to be playable, because files show King Boo's icons and other stuff as "kingboo" and "teresakingu". Meaning that the "teresa" folder and the file can't be for King Boo, but maybe Boo.
Unused files are called "silver_kato" and "gli_silver", meaning Silver Kart (because "kato" or Käto means Kart in Japanese) and Silver Glider ("gli" is supposed to mean glider). These files show icons of a Silver Standard and a Silver Glider. So the Silver Standard was going to be a kart, as well as the Silver Gliders were going to be part of the kart bodies.
Another folder is called "heartcoach", obviously meaning the Heart Coach was going to be a kart body. However, the folder show some files that doesn't have any data.
In early screenshots, there was going to be a kart called Banana Booster. The kart is a banana-like specie of boat, having tiny windows at the sides. It got scrapped of the game for unknown reasons.
A file shows the name "oyamalab_course" meaning that E. Gadd was going to have his own race course, resembling a Laboratory, since "oyama" is his name in Japanese, with "lab" meaning laboratory.
- Track Logo
- As seen in the beta icon, the Poison Mushroom was going to take it's look from Super Mario All-Stars, being purple with a skull on the front.