I found this out on a website, but I accidentally lost it and I can't remember what it was called. Anyway.
If you zoom in as much as you can on the Metal Mario trophy, you can see a reflection of the Yoshi's Island (not Yoshi's Story) stage on his hat.
I'm sure most of you know this but in early copies of SSBM you can see an extra eye on the Daisy trophy. Also if you zoom up Peach's dress (in the adventure mode trophy), you can see her panties, xD.
In a tag battle, if your partner has two lives left and you have lost all your lives, press start and your teammate will have one life and you will have one life.
I'm sure most of you know this but in early copies of SSBM you can see an extra eye on the Daisy trophy. Also if you zoom up Peach's dress (in the adventure mode trophy), you can see her panties, xD.
on the Corneria and Venom stages, Fox and Falco can summon their Starfox allies by pressing left and right rapidly on the d-pad, and Slippy, Peppy, and Fox/Falco will say a bunch of meaningless dribble