Archive Panic: He has more than 1,000 stories on Fanfiction.Net alone which would no doubt take an immeasurable amount of time to get through every single one. To make matters worse, some of them have an obscene amount of chapters which are constantly being added. The two busiest fics are Waluigi's Taco Stand which has over 500 and Life at Pizza Hut which has officially surpassed 800!
Dork Age: Had an Attention Whore period roughly around 2010 where he would deliberately post fics in the wrong sections of Fanfiction.net (Such as putting a Mario story in the Beavis And Butthead section), all of these "dishonest" fics have since been rethemed, deleted, or replaced.
Hilarious in Hindsight: He wrote a fanfic about the Nintendo characters (along with Spongebob Squarepants characters) going to Universal Orlando. Guess what happened nine years later (and earlier for the Spongebob crew).
Yoshi Kart has a slew of this. The Koopalings joined in on racing against Yoshi and friends almost a decade before they would do so in Mario Kart 8, which also had Link racing alongside the Mario characters. The Koopalings would later race alongside Bowser Jr. in the upgraded rerelease dubbed Mario Kart 8 Deluxe. Sonic and Banjo would race each other in Sonic and SEGA All Stars Racing, with this being the first time Mario and Sonic characters would compete with each other in a racing sport.
Padding: A common criticism is how much he spams his fanfics and chapters out, as it not only pushes other authors' stories off the front page, but his own as well. Roughly a third of his stories have few or no reviews because they often get bumped into obscurity before they can even be read.
Recycled Script: Subverted. Some of his stories start out like this, only to completely end up differently.
So Bad, It's Good: The appeal for pretty much a solid chunk of the fanfiction he writes.
What Do You Mean, It's Not for Kids?: Some of his works are rated M. Although there are a few snippets in his T rated fanfiction that have small traces of stuff that aren't appropriate for kids to read.