SMG4: Welcome To The Kushroom Mingdom is a blooper by SMG4 released on April 8, 2017. In this blooper, SMG3 has decided to create his own bootleg dimension, and it's up to Mario and crew to figure out what's going on.
The plot starts with Luigi searching for Mario under Peach's dress. Regardless of where he looks, he still can't find him, he then pops out of Toad's afro. When Toad asks why he was in his afro, he tells him that Mario's been missing for a long time. As Mario aggravates him, Toad gets really happy.
Suddenly Luigi found Mario's clothes scattered across the floor and then he saw a Toad Gnome next to Mario's hat. Luigi thinks that Mario somehow became a gnome.
Toad Gnome jumps to the wall and teleports to another dimension. Luigi follows after him and all of a sudden, he found himself in the Kushroom Mingdom, with most of the inhabitants are bunch of messed up beings. Luigi then saw SMG3's Castle and approached it where he meets none other than SMG3 himself. SMG3 reveals that he caged Mario and gave him lots of spaghetti, to his great pleasure.
Luigi tried to escape and seemingly succeeds in holding off SMG3's army, but Shrek (who serves as SMG4's counterpart in this dimension) sits on him. He too is captured. Luigi asks Mario to come up with an escape plan as he is the main character (apparently unaware that he IS the main character of the video), but Mario simply munches on spaghetti.
Luigi attempts to persuade SMG3 that he shouldn't lock up both Mario and himself, as people would be worried regarding their disappearances (even though Toad appeared to be ecstatic that Luigi had gone missing as well). SMG3 explains that he managed to build his own kingdom using a wish from Grand Dad, and that he only needed Mario and Luigi to complete his kingdom.
However, the way he worded the wish (to have a kingdom just like the Mushroom Kingdom) backfires when Bowsur shows up and demands SMG3’s princess (who is actually Old Man Hobo).
SMG3 commands Toad Gnomes to attack Bowsur, but this only provoked him to set the castle on fire. Taking advantage of the situation, Luigi persuades one of the Toad Gnomes to release him. He then frees Mario and the two flee, only to encounter a hallway filled with Toad Gnomes. After Mario's failed attempt to sneak past, Luigi makes the Toad Gnomes think that Old Man Hobo who disguised as the princess wants to make love to distract them.
SMG3 commands Bootleg Kamek to prevent Mario and Luigi from escaping, but it backfired when his spell strikes Bowsur instead. Bowsur grows enormous and sets fire to the entire kingdom. SMG3 swears revenge on Mario and Luigi though they’re not actually responsible for the destruction of his kingdom, just before Shrek crushes SMG3 by sitting on him.
Mario and Luigi escape the dimension. Mario then blocks the entrance with a chair and the two leave to relax. Toad is dismayed that Mario and Luigi returned in less than a day. Shortly afterwards, Toad discovers a hat that one of the Toad Gnomes left behind and becomes a Toad Gnome himself.
italics denotes that the person presumably dies in this episode.