This is one of the reasons why I recommend Tunnels & Trolls to any person who has or hasn't experienced rolegaming: Because the most nonconformist and, perhaps, dangerous ideas seem to run through TnT (the preferred acronym, which does imply its danger) first.
Yes, there have been humorous scenarios before, going all the way back to Blackmoor. Yes, there have been humorous solos, going at least as far back as Deathtrap Equalizer Dungeon.
Despite the precedents, there has been nothing quite like Fleabitten, and I don't know how to categorize it.
It's humorous - a lot! And it has the sort of absurdist logic of Lewis Carroll. It's deadly, but only if you treat this adventure as you would most RPG adventures. And it's a solo, which can be adapted for GM use, especially if the GM is just a little bit cracked.
The main track (which you may choose to not take) concerns an underwater adventure of discovery and deduction. You will discover a new type of dwarf and a LOT of things about undersea life that you never suspected. And you would, if this were a Call of Cthulhu adventure (and it could be), lose a lot of Sanity Points.
As always, Mark provides options to options and options OF options. Almost every action has a consequence, and the characters (though absolutely ridiculous at times) usually come off as 3-dimensional - save for those who are not intended to seem realistic at all.
You'll interact with some of your favorite fictional characters from comics and elsewhere...though they may seem a bit more eccentric than usual. They may even carry different names and forms. It's always a toss up whether Mark is seriously challenging your sense of humor, your sense of honor, or your gaming skills. Few people can pull off a comedy which is equally an adventure, or vice versa. There is a difference.
Steve Jackson, decades ago, gave one of my favorite sayings when he stated that there's just not enough silly in games right now. Of course "now" was THEN, but I hope you get my meaning.
And if you understood that last paragraph, much less the previous ones. "Fleabitten" is for YOU.
You'll find it in the usual downloadable places, such as DriveThruRPG/RpgNow, and nowhere else of which I know. But you can always write Mark and annoy him to death. It would serve him right!