Things you didn't notice before in Mario games

Koopa Shell noises in MK are meant to sound like the noises Koopas make
Wait...
Does that mean they're still in there?
YOU GOTTA TELL THE WORLD THAT KOOPA SHELLS ARE MADE OUT OF PEOPLE
 
I have him unlocked in Smash 4 and...I don't quite recall that's how you unlock him

HNI_0025.JPG
 
In Yoshi's Crafted World, Red Coins spin the opposite direction of normal coins. Haven't checked any other Yoshi games yet but I think it's unique to Crafted World.