It has lost its appeal
I used to like this series around when it started. Now that my standards are higher, well, this isn't entertaining anymore.
The reason for this is that my main appeal to this series was how you animated sprites in fight scenes. Now that this series is on it's 7th episode, the fight scenes are seriously getting repetitive. The action here was pretty much the same action scenes as before, with the same sound effects as before, and some slightly different angles. They just aren't interesting anymore. Although, the 8 bit action scenes were more interesting to watch due to the fact that sprites moved more fluidly. I'm going to assume that you did create those sprites yourself, and didn't just use somebody else's, because if you did, than that just means you downloaded the sprites, imported them into flash, and used them to create a repetitive fight scenes, which doesn't take enough effort.
There was just plainly too much text to read in this one, especially one that just simply boils down to a bunch of clichés. Some dialog I skipped because it's poorly written, and unnecessarily long. It's hard to take the plot and dialog seriously, and it always has. I mean, it's a story crossing the Mario universe with the Sonic universe together. That has always been uninspiring and unoriginal even at the time of Episode 1, but I was able to forgive the plot at the time because of the action scenes. But now your just pushing the cliché level far enough, and like I said before, the action is now repetitive unappealing.
The humor is non-existent, with most of the jokes were based off of Luigi getting hurt and being a pussy. You overdid this joke too much in the series, especially in this episode. Other jokes had also been overdone, such as the overused fourth wall break after yet another overused and not funny joke about "Over 9000". Adding sound clips of catchphrases from TV shows is also not funny. I didn't laugh too much in any of the previous episodes, but this episode desperately forced too many unfunny jokes, which ended up embarrassing itself.
There were some parts with regular animation (rather than sprite animation) and they looked nice (Although unfitting for a Sprite animation) and I believe it shows that you have potential for creating decent regular animations.
I suggest you at least try to make a non-sprite animation for your next flash (one that preferably doesn't involve Mario or Sonic) because this series is getting repetitive, cliché, and old.