The Super Smash Bros. series has featured a lot of characters across its three titles, but they won't all return for the next iteration. They simply can't according to designer Masahiro Sakurai -- there just isn't enough time.
Speaking to NowGamer, Sakurai laid out the reasoning behind the decision. "Adding new characters is not a simple addition -- it’s really multiplication. The amount of work, adding a character is multiplied and becomes bigger and bigger as you go. We can’t because of the amount of work it takes."
Sakurai appeared to lament the fact that some players' favorites would be omitted. "We're going to put in as many characters as we can, we really want to do that, because it's good for the fans and good for all of us. But in the event that we do have to cut some characters, I'd like to apologize in advance to those fans" he said.
Look on the bright side: if you find yourself without your Super Smash Bros. favorite, you can just pummel your opponent into submission with the Wii Fit Trainer's yoga moves.