In "Super Mario Bros. 3" there are Pile-Drivers which are blocks that hop around. I've always thought it would be cool if in a future "Mario" game there were all kinds of blocks with legs and Micro-Goombas so Pile-Drivers could be question blocks, grab blocks, ice blocks, indestructible blocks, etc. I also think there should be other colors of Koopa Troopas (based on my inadvertent discovery of the Black Koopa Troopa, and the possibility of a grey one also existing).
Mega 2
Cybernetic Abiogenesis Project