A few of the enemies are from Kirby games.
That would make sense, since it's Meta Knight as (what seems to be) the bad guy.
Meta Knight isn't the bad guy actually, judging from Sakurai's little hints. For example, after revealing the Battleship Hallberd stage, he said:
It has arrived! The Battleship Halberd! It’s Meta Knight’s battleship...isn’t it?
That implies that it probably isn't under Meta Knight's control. Then after announcing Meta Knight as a playable character, he said:
It's Meta Knight, whose introduction was delayed for some reason. He's Kirby's...rival?
Which seems to imply that Meta Knight may not be Kirby's rival after all.
We'll HAVE to do a Brawl tournament here at GW.
I say a few weeks after getting Brawl and unlocking most of the stages/characters and after getting used to the game, we hold an official GW Brawl tourney. Yay or nay