"Darkness Takes Over" is SMG4's 13th blooper. In this video Mario is bored, so he buys a cannon, shoots himself out of it, and accidentally breaks the Sun. The world becomes shrouded in darkness, so Mario has to recover the Sun by going completing various puzzles.
When Mario buys a new cannon he accidentally takes out the sun and makes everything dark. It is up to him to fix the lack of light in the world.
The blooper begins with Mario leaving his house to combat boredom. He tells Luigi that he is going out, which Luigi does not initially hear because he is listening to "Party Rock Anthem". Mario goes to a shop in Toad Town, and when the shopkeeper tells him that they have a sale on the Super Ultra Cannon 9001, Mario decides to buy it (using money from Peach's bank account).
When the cannon is about to arrive at the castle, Mario celebrates loudly until Toad asks him why he is screaming. Mario tells him about the cannon and how he paid for it. He says it is fine because Peach loves cannons, to which Toad replies that it is only true when they are aimed at Mario's face. At that moment, the cannon is delivered, and Mario signs for it. Expressing surprise at the cannon's size and how he is supposed to install it, Mario is told to call an engineer.
Mario complains about this to Toad, until Toad explains that Lakitu is an engineer. Lakitu grudgingly agrees to install the cannon for Mario, and soon does so. Mario almost immediately decides to try out the cannon, first by testing its range of motion. Then, he decides to fire it, picking the sun as his "perfect target". He launches out of the cannon and somehow breaks the sun in the process.
Mario tells Toad that he broke the sun, to which Toad reacts with shock and disbelief, saying that it isn't possible. After some discussion, they feel strange, violent shaking, but Mario brushes it off and decides to go to sleep. However, when Mario wakes up, he notices that the entire landscape is covered in darkness, and that the sky is glitched. He checks inside the castle and in other games, and notices that the darkness has spread there as well.
Almost immediately, Mario asks the Strategy Guide for help, but it tells him to figure it out himself. It does tell him, though, about a portal that can only open with some kind of source. Mario suspects that Bowser might know what that means, and goes to his lair, which is surprisingly unaffected by the darkness. He asks Bowser why this is, and Bowser says that he used a light bulb. Mario realizes that a light bulb is a light source, and thanks a confused Bowser for the information before leaving.
Having formed an idea, Mario goes on top of the castle. He tries to get Yoshi's attention, which takes a while because Yoshi is also listening to "Party Rock Anthem". He tells Yoshi to contact Luigi and Wario, to have them all meet under a haunted mansion, and to bring a light bulb. After some planning, the four of them try to get said light bulb to a socket without getting attacked by Boos. Mario does almost nothing to help the others, and is called out on it, but, after the light bulb is activated by Wario, he claims the credit for himself.
Mario then goes to Bob-omb Battlefield to search for a portal, and one of the Bob-ombs says that there was a strange noise on the summit. Mario reaches the summit (and somehow switches to a Pokemon game in the process), and sees the portal. He watches as a shadowy figure emerges from the portal and orbs of light enter it, all the while commenting that he can't understand the text because it's written in another language.
Mario enters the portal, which he says reminds him of a toilet, and ends up in another location. He walks along some floating platforms and enters into a battle with a Giratina. He tries to battle it the right way, but then gets bored and decides to take the easy way out - shooting the Giratina with a machine gun. He celebrates his victory, but gets out of the area quickly when police show up and try to arrest him for "Pokemon slaughter".
Mario makes his way back to the castle, and sees that it is back to normal. He told Toad that he had done it, but then Toad revealed that Lakitu found faulty wiring, and that he had fixed it. Mario becomes annoyed, but then he hears Peach outside getting into the cannon and saying that the sun is the "perfect target". He hears another crash and the castle becomes dark again, and he says that he isn't fixing that.