SM64: Bad Star's Back! 300k special, more often simply called Bad Star's Back!, is the 215th video made by SuperMarioGlitchy4, specially released to celebrate him reaching 300,000 subscribers on YouTube. In this blooper, 10 months after the events of "Bad Stars", the evil Ztar comes back, and Mario and SMG4 have to fight him again.
Still on the cruise boat at Delfino Plaza, the Ztar mutters how he's had to deal with 10 months of singing by the Old Man Star and Justin Bieber, and he asks for more since it's so "nice" and the Good Star continues to sing, and sings so loudly and badly that many citizens of a nearby town begin dreading the noise, fainting and some even exploding at the sound. The Ztar yells that it was sarcasm, and rips his chains free, which horrifies the Old Man Star, who is then shot with a laser by the Ztar, who laughs evilly before being taken over by his Toad personality.
In the castle, Mario is enjoying a plate of spaghetti when some black and white people barge into his door after knocking. They query him about the bad star, however Mario doesn't care what they want because he's busy with his spaghetti. They ask for his help since the star has already started its reign of destruction and they need it badly. Mario asks what he would get for it, and they reply that he'll save the world. Mario doesn't care and continues eating his spaghetti. They knock him out, and take him to their base.
He and SMG4 (who was also captured) wake up to find themselves in a base. The boss of this base asks if they've had an experience with a bad star, and Mario replies they thought they sent him on a "boat trip from hell." The boss tells them that it has expired and shows them a video which shows the Ztar going around causing mayhem while singing a song about the "candy land," the video demanding he needs stars if they're unwanted. He asks if they're going to help save the world, Mario instantly replying no, and SMG4 punches him.
Meanwhile with the Ztar, he's flying in a hilly region and ends up having trouble maintaining his normal personality, and decides to call the Teletubbies for assistance in his plans.
Mario and SMG4 in town crash their car and try to confront the Ztar. The ground shakes, flinging Mario all over, and the massive Ztar stares at them from above, and fires a laser at them, which misses. SMG4 screams to Mario if he's got an idea, the latter deciding to lure SMG4 into making him become a humping target for Mario. SMG4 questions what this will accomplish, and Mario replies that it won't accomplish anything, and humps SMG4. The Ztar fires a Bullet Bill at the duo, flinging them onto the ground harshly. The Ztar closes in on them mocking their attempts to defeat them, before being taken over by Toad, which Mario remembers and realizes. The Ztar can't take it anymore and summons his backup team, and the Tubby Bison shows up, which doesn't threaten SMG4 and Mario all that much, until they get surrounded seconds later by more of them, all with weapons. The Ztar flies off, leaving them as a distraction while he continues to destroy the world. The duo aren't pleased in the slightest.
At the castle, Toad angrily yells at Peach on the roof and warns her of the incoming star, as it rises over the horizon. Peach screams for Mario to help her.
Back with Mario and SMG4, the Teletubbies are trying to teach them the alphabet, which annoys SMG4 to the point of him banging his head against a table, while Mario actually tries to remember it. They ask him what comes after Q, and Mario replies that the answer is W, which is incorrect, and causes the Teletubby to draw his katana and runs at Mario. Mario dodges the sword and kicks it back into the Teletubby and it stabs him, Mario and SMG4 remark in shock, and all the Teletubbies begin attacking them, and the two fight their way out, defending each other and using whatever maneuvers they have until they're all defeated, the final attack being the two holding guns at the Tubby Bison, who remarks with utter frustration.
Back at the castle, the Ztar has already eaten the Stars of the castle, causing him to grow to massive proportions and asks for more from Peach, who tells him she doesn't have any more, but she has star-shaped biscuits if he wants them. He yells at her he needs more as the duo arrive, their faces in horror. SMG4 has an idea on how to defeat it, and, with his Cannon Penis, he shoots Mario at the Ztar, who stops his fall and begins to suffocate Mario while in his field. Peach and SMG4 become worried, the latter running to save his friend. Toad comes along on the way and asks SMG4 if he would like to make him macaroni, making SMG4 yell at him to distract the monster, but Toad refuses. SMG4 doesn't care and kicks Toad into the sky, and he takes Mario's clothes off when he hits him, which horrifies the Ztar and it makes him stop. Mario hangs onto the Ztar, who is horrified that he's naked, and he becomes more frightened when Mario grabs onto him. SMG4 calls the Old Man Star, who is having a bath at the same moment, and delays his arrival by 20 minutes, which doesn't please SMG4, who needs to find a way to distract him for a little longer.
Meanwhile, SMG3 had been sleeping for a majority of the day, and he sees the Ztar with the naked Mario holding on for dear life on it and decides to go back to sleep.
They end up in the city again, and crash into the ground, knocking Mario off the tremendous Ztar. The Ztar is absolutely furious with what Mario did with the grabbing him and the recently-discovered dead Teletubby army, and rains bullets of fire down onto Mario, who covers with a dead Teletubby to protect himself. SMG4 on a building throws a Star to Mario, to catches it. The Ztar demands several times to Mario to give him the star, who refuses each time, even when Peach is threatened. The Ztar gets enraged and closes in, as Mario tries to use the Star but it doesn't work, so he kicks it into the Ztar thinking it won't work on him either, and he spits it out, calling it "disgusting." The Star reveals itself as the Old Man Star, and SMG4 reveals he painted it as a disguise so he would stay. The Old Man Star then creates a portal, and the Ztar gets sucked in. Seconds before it gets sucked in, Mario yells at the Ztar if it likes spaghetti, and the Toad personality takes over, yelling spaghetti as Mario throws a plate into the portal, with the Toad Ztar flying in after it, and the Old Man Star disappears too. The portal disappears, and SMG4 asks Mario if he'll put some clothes on, who instantly refuses, and decides to go and get food, and the two display their pleasure that it's over, as the video ends.