Palutena fake-out, Ridley's shadow, and Meta-Knight's stage come to mind.
EDIT: And I'm sure this has already been mentioned by now, but you can also see a part of Ridley's wing (?) when the shadow goes overhead. The color isn't purple like normal Ridley, but more of a grey/silver. However, people have attributed it to Ridley's tail from Other M, though apparently that's not really Ridley in-game so... square one.
There is a Kremlin during the Smash Run, so yeah. King K. Roll Krash the Kerfuffle
All aboard the hype train. And Sakurai love to put secret in his games, so Jigglypuff, Captain Falcon, Ness are all probably coming back as secrets. Mr Game And Watch too maybe. The roaster will be really good if he even put 6 secret characters in.
I'm not even sure what this is supposed to be saying. Those four trophies are from four of Nintendo games and this person seems to think they are the most discussed games as far as new characters are concerned. That's it? Nothing was said with that image, unless I'm missing something.