SMG4: War On Beeg SMG4 is the nineteenth episode of Season 10 and the five hundred and seventy-third overall to be uploaded by SMG4.
This video introduces Shroomy's Anti-personality. It was aired on May 23rd, 2020.
Looks like Mario has a beeg beeg problem.
The coming of Beeg SMG4 is causing the world to panic. At Clock Town of Termina, Hal Monitor, Bob, Link, Chris, and Swag attempt to stop it, but fail. Meggy hides in a trash can, claiming it's safe and Beeg SMG4 will not see her in there. While Axol is watching his anime, he sees Beeg SMG4 through his window. Axol closes his curtains and continues watching anime.
Saiko watches Chris and Swag attempt to stop it and remarks that they need to launch something with the power of ten nukes at Beeg SMG4. Shroomy then tells Saiko that he finished his rocket. He launches his rocket at Beeg SMG4.
Mario launches JubJub at Beeg SMG4 with a catapult, but he accidentally knocks out Shroomy's rocket, causing Saiko to get angry with him, telling him that it was "our one chance to save the world".
Mario, Saiko, and Shroomy later head over to Kennedy Space Center of NASA at Florida for help from Professor E. Gadd, passing by some research about Beeg SMG4. After interrupting E. Gadd from his anime, E. Gadd tells them in order to take down Beeg SMG4, they need to find a being of similar godliness. E. Gadd then proceeds to tell them about a place to find demons in, the "Upside-Down Dimension" (otherwise known as Hell by Shroomy). E. Gadd pushes Shroomy, Mario, and Saiko into the Upside-Down Dimension, and tells them not to come back until they find a demon.
Once Mario, Saiko, and Shroomy reach Upside Down, they see a dragon take The Villager, and Saiko asks "what the hell is that?". Saiko then angrily asks why crap like this happens to her when she's with Mario, to which Mario shrugs his shoulders. Shroomy gets out his banjo and starts strumming a little ditty about walking through the Upside Down with his friends. After the song, Shroomy gets snatched and thrown to the ground by a demon. After seeing Shroomy get attacked, Saiko hits the demon with her hammer, but it doesn't do anything. The demon throws Saiko to some rocks and then another rock falls on her, rendering her incapable of moving. Mario charges at the demon and then offers to buy him dinner, but the demon blows fire at him. Shroomy asks the demon to stop killing his friends, but the demon grabs Shroomy and holds him tight. Shroomy realizes his own predicament, sees Saiko trapped under the rock, sees Mario aflame, and then realizes he needs to stop the torture he and his friends are going through. He then says he doesn't want to let his demon hunter self out, but after he sees the demon about to hit his butt, he lets his anti-persona out. Shroomy turns blue and has a sinister expression on his face. Anti-Shroomy throws the demon to the ground, causing an explosion. After Anti-Shroomy taunts the demon, he rips off the demon's hand and throws it, causing the demon to scream. Anti-Shroomy further attacks the demon while Mario and Saiko watch in amazement. Anti-Shroomy hits the demon with the demon's severed hand, causing the demon to scream and run away. After Anti-Shroomy taunts the demon one last time, Anti-Shroomy turns back into Normal Shroomy. Saiko asks where Shroomy's skills came from, and Shroomy replies that it was "old habits coming out, I guess". Shroomy then reveals that in a past life, he was a demon hunter, but now he's a boy Scout. The portal to the real world opens and Professor E. Gadd returns, asking Shroomy, Saiko, and Mario where they've all been, for time was running out. Shroomy explains that they couldn't capture a demon, but they did keep a demon arm. E. Gadd says that there is no other option.
Beeg SMG4 looms over the sky, causing people of Termina and Mushroom Kingdom to scream in fear. Back in the NASA lab, E. Gadd throws the demon arm to the side and shows Saiko that he has SMG4's DNA. Shroomy asks why E. Gadd has SMG4's DNA, but E. Gadd orders Shroomy to be quiet. E. Gadd puts the DNA next to the demon arm and performs a ritual, causing another form of SMG4, Long SMG4, to appear, who kicks Beeg SMG4 into outer space. Saiko, Mario, and Shroomy celebrate. Shroomy questions E. Gadd about Beeg SMG4's arrival. In the flashback, E. Gadd looks at all the Beeg SMG4 memes, claiming he doesn't need them. But then E. Gadd can't hold it in anymore; he needs Beeg SMG4. Desperate to see Beeg SMG4 for real, he kidnaps SMG4 and fuses him with Beeg Yoshi. Out of the flashback, E. Gadd lies to Shroomy and claims that SMG4 ate too much spaghetti. Mario wonders what will happen to SMG4. Meanwhile in outer space, SMG4 reverts back to his normal form, and is relieved that he is not Beeg SMG4 anymore. He is now aware he is now stranded in outer space, and is mildly disappointed. Along comes Link, on Epona and Master Sword in hand, screaming.