Through data mining and various other overtly complex methods, an avid fan of the Super Smash Bros. series has uncovered some unused texture files in Super Smash Bros. for Wii U that point towards plans for Dr. Mario to have his own stage at some point during development.
The three viruses pictured look as though they could easily have been an Assist Trophy that was scrapped during development, but further delving brought about three placeholder character icons for each virus variation. These icons are used to denote KOs on the results screen, and every playable character has one as you might expect, but so do Metal Face and Ridley. This heavily implies that these three critters were intended to be used as boss characters on a stage much in the same way as Ridley, Metal Face, and the Yellow Devil are in the final game, and boss characters require a stage.
We can only speculate what the viruses would have done, or indeed what the stage may have looked like that would house them, but nevertheless it's always interesting to see ideas developers have to cut from the final version of their games.
What do you think these viruses would have done in the game? Let your opinions burst forth in the comments.