Retro an E3 2003 demo build of Mario & Luigi Superstar Saga has been found and dumped.

[Krvavi Abadas]

from a new preservation group known as "CodeBound", the source for the cart seems to be a collection from AlphaDream, who might have thrown out all of their development stuff after the studio shut down in 2019.
as the same group also released a prototype of Hamtaro: Rainbow Rescue a few days prior.

normally this build is locked to 3 specific moments of the game intended for demo purposes, but it's fairly easy to edit the "save files" and change the location to somewhere else. which shows a pretty solid chunk of the game is still left in the data. though the only parts that were (roughly) translated to English is the normally accessible content, with everything else still being in Japanese.

one notable find so far is that a few of the brothers sprites use an earlier version of their design, most notably featuring blue eyes.

which matches up with concept art that was shared by Isago Fukuda (credited as a "Sound Engineer" in this game, but he is noted as doing graphics for AlphaDream's first title Koto Battle: Tengai no Moribito) a while ago.

 

[Catsylvania]

The art of Mario and Luigi with the soulless blue eyes is haunting.

The blue eyed sprites look good though. I get the change for consistency with the final art.

 

[Gabev]

Nice, my favorite Mario RPG.

 

[Clov]

That placeholder Bowletta sprite looks so funny. She's so mad!

 

[Luneth]

God, I have to say that even if I liked the improvements, I love so much more the GBA sprite artwork than the 3DS 3D graphics. It's just magical.