Originally posted by ThomasRename your ROM to "game.smc" instead of .sfc.
In case you're wondering why, it's due to a header in the ROM file (512 bytes inserted at the start of the file). Asar detects whether a ROM has a header or not by checking the extension; SMC files have that header, SFC does not. Lunar Magic automatically adds a header to ROMs if they don't already have one, so SMW hacks will generally be headered and thus use the .smc extension.
Where can I get whatever that is?