Angry Sun was in the base game files, actuallyRemember that piece of artwork for the first game which showed a bunch of sprites and one of them was SMB Yoshi? Too bad nothing came out of that. The Goomba Shoe and Stiletto were probably used as fill ins.
I think DLC would have been happened if the game came out sooner in the Wii U's life. I think data for the Angry Sun was found in one of the update files.
also the big iron ball that bowser in the clown car used to throw
part of me wonders how much of SMM2 was originally considered for SMM1 DLC before they pulled the plug because wii u.