I saw a youtube video(yes, it was a tas but didn't specify if it was on an All Stars + SMW cart/rom or not) and mario died at one point in a glitched castle with SMB3 music playing and with the SMB2 death sound. If you can, what happens? Can you access a "minus world" of some sorts from the data of the other games? I know you can, using ACE, write songs that use another games soundfont and stuff like that but not loading entire levels from separate games.