Developer:A myriad of hackers working in collaberation in this forum: http://talkhaus.raocow.com/
A Super Mario Thing is not your average Super Mario World hack.
It all started several years ago on the Something Awful forums with a Let's Player called Raocow who is reasonably well-known in the LP community as a love him or hate him, stream of consciousness LPer who is prone to non sequiturs and has a strangely hypnotic voice aided by his French Canadian accent. Over time he developed quite the following and eventually made his own site with it's own forum, http://raocow.com/ and http://talkhaus.raocow.com/ respectively.
Much of his following are avid Mario players and hackers themselves and they asked him if they made a hack if he would LP it. He agreed, but only on the condition that it be a good enough hack that he would want to play it anyways. Over the course of several months the game was developed in a collaborative effort headed by one user with the name yoshicookiezues along with several other experienced hackers. The resulting hack is a very unique and very difficult at times game, which Raocow LP'd to completion prior to game's release.
On Super Mario Central the game has mixed reviews, mostly due to the difficulty being up there, but that's part of the game's charm. The game is also stuffed to the gills with references to Raocow as well as other hacks such as the Vip series (in fact, Raocow has been quoted saying that ASMT was his forum's Vip).
I personally love the game. It's the sort of widget of a really strange game that is at the same time fun to play that would be good to review just for the reviewer.
A sequel is currently in production that is planned to lower the difficulty and the amount of references to Raocow brought down (to finish the quotation I made before, ASMT was Talkaus' Vip, ASMT2 will be their Super Mario Yeah, another game he's LP'd that was creative and weird without being nut bustingly hard) to make the game more accessible.