I may have found some images of the goomba in Mushroom Kingdom Showdown. This may not be true.
EDIT: More pictures, 2 more.
EDIT: Even More Pictures! 3 this time!
FINAL EDIT: Ok, I admit it that this leak is a fake. Most of you guessed that anyway. Now finishing up this leak, I am going to make a sprite sheet for goomba that wwwwario can use if he ever makes him. (they may have I see a 4th unlockable in v0.7)