User blog comment:Tadmonkey/Things I dislike about Smash Bros. 3DS/@comment-25476555-20140928212920/@comment-4151849-20140928232513

I highly doubt that Sakurai woke up one morning and said "Hmm, I don't want to put Mewtwo to be in the next Smash, I'll bring Dr. Mario back instead". Dr. Mario isn't taking up the slot of any character, he's just a fun addition. In fact, slots don't even exist.