Alvin gone on record stating that he feels that the series dialogue in general is "godawful".
Alvin has said that he is not proud of Episode 7 outside of the 8-bit parts. It had too much dialogue, the exposition involved was completely pointless since that had nothing to do with overall plot, and the ending with Kolorado's stopwatch was a major Deus ex Machina.
Despite positive fan reception, Alvin regrets creating Basilisx because his presence was shoehorned in due to lacking proper buildup and backstory.
Creator Breakdown: This has happened a couple of times in the original run, due to fans pressuring the release date of the next episode. One of the times Alvin-Earthworm had one, he temporarily canceled the series. Thankfully, he made an apology and uncanceled it the next day.
He's now having one during the reboot, due to continuing physical and mental health issues that have left him unable to do much work on the series, which has in turn exacerbated his mental health issues as he's upset at having let his fans down.
One of the most popular theories for how Mario would be saved from Basillix involved Luigi using the power of his Tanooki suit to recover from Basillix's stone gaze. The first scene for the unfinished Episode 9 reveals that this is indeed what was going to happen.
Portions of the fandom expected Alvin to cancel the series due to how long he was taking with each episode after 6, especially when he kept insisting that he wanted to do 3 sagas in 15-episode installments. Much to their dismay, he did. It took three years for Alvin to decide to bring back the series as a reboot/retool.
Schedule Slip: Suffered from this terribly in the later episodes, and somewhat ascribable to Creator Breakdown. There was a 16-month gap between episodes 6 and 7, a 12-month gap between episodes 7 and 8, and a 30 month gap between the release of episode 8 and the original series' cancellation.
The old anime-style opening became this after the original run of the series was discontinued. It showed off a lot of characters that were meant to appear in future story arcs.
In the original run, episodes 1 and 2 were meant to be a single episode, as were 5 and 6. Alvin had to split them into two due to software limitations at the time and pacing, respectively. The revival was episodes 1 and 2 made into a single episode as originally intended.