Pure awesome!
Wow this really tops what you have done so far! I love the story and all the twists and turns it takes, and the characters are very fun and well developed. I like how you keep Mario and Luigi true to the games by not giving them dialouge and leaving that to Sonic and Shadow. The action is also very fun and has an internse pace to it. I found your use of the Minus World to be very amusing, and I couldn't help but laugh seeing them in 8-bit form. While i was suprised in how long this episode was, the length of it didn't bother me at all.
You have really done an outstanding job with this series and I am eager to see the next episode to see what happens. I just hope Luigi gets a chance to shine and show some power.