Master Hand is a recurring character in SMG4's videos. Instead of Sakurai, he created Super Smash Bros.
Master Hand was originally made to be a mutation of Mario's left hand that appeared in Have you seen this Polygon? and made a cameo appearance in Flashbacks. After losing his left hand and blasting to Final Destination, Mario realizes that he has to defeat Master Hand in order to regain the appendage. SMG4 soon scratched the idea of Master Hand being Mario's hand, and instead gave him the title of the God of all games.
Master Hand's main attacks are smashing, handguns, walking, farting, and saying bad things. It seems his favorite food is ultra peppers.
Master Hand reappears in R64: Stupid Smash Bros, where he is the main antagonist. Master Hand constantly demands Mario the Smash Ball that he lost and got stolen from him. Mario disobeys the hand, causing him to send fighters and mind control people from the Mushroom Kingdom to fight Mario until he gives up the Smash Ball, however, all of them are retarded and too stupid and useless to even fight. This causes Master Hand to go crazy to the point he does the entire thing for himself, weakening Mario, but is even defeated by Ganondorf, in his Beast form, to charge after him and knock him offscreen.
Master Hand appears again in SMG4: Mario Battle Royale, as Game Master of the new Battle Royale mode. After playing a game similar to Fortnite, Master Hand gives Mario a Chicken Dinner as a reward for winning. Master Hand then revives all the players Mario killed for a second round, and Mario is, well let's just say they payed him back.
In The New Smash Bros, Master Hand gets Arthritis so Crazy Hand takes Smash Bros. He however gets better during the Adventure mode and takes back Smash Bros. He then appears in Vs. Master Hand mode with multiple firearms because he's still sick, leading to Mario committing suicide.
Waluigi begs Master Hand to let him in Smash Ultimate in SMG4: Waluigi's Time, but Master Hand tells him that he needs to have a Special Move before he can let him in. Waluigi soon discovers his Rejection Powers, and demonstrates it on a Teletubbie worker. After seeing how powerful Waluigi's Rejection Powers were, he decides to let him in Smash. However, due to Waluigi being accepted, he loses his Rejection Powers, and is once again rejected. After rejecting him again, Waluigi went insane and swore revenge on him and the rest of the world. That being said, he is technically responsible for the events in SMG4: Mario And The T-Pose Virus, and even became a T-Pose zombie before being revived by Peach.
In SMG4: The Mario Convention!, he tries to stop Waluigi from proceeding with his takeover, but Waluigi shows off his new power: Mind control. With it, Waluigi tortures Master Hand and makes him worship Waluigi as his master.
In SMG4: Mario and the Waluigi Apocalypse, he is acting as the general of the T-Pose army. Tari, who had hid in a nearby cart searching for a duck while Waluigi attacked the Convention, had tried to snap Meggy out of her T-Pose form, but was unsuccessful due to Waluigi's power. Master Hand spotted Tari, and attempted to kill her, and Tari threw everything she had at him attempting to fight him off, but nothing seemed to harm him. One of Tari's items, a NES controller, had collided with Waluigi's scepter, and gave it the powers of Mind Control. With her NES controller in hand, Tari now had full control over Master Hand, and made him do a bunch of hilarious things like dance and strike a peace pose shouting "KAWAII". She eventually lost control over him after Waluigi returned and made him attack SMG4, Mario, and Saiko, who were driving in the Death Bus. Saiko smashes Master Hand with her hammer, but Master Hand eventually grabbed her and helped Waluigi turn her into a T-Pose zombie.
He later appears in SMG4: Mario's Big Chungus Hunt. After Mario threw Shigeru Miyamoto out of a window to eliminate Big Chungus' competition, Master Hand started reprimanding the plumber for his action. Mario used a killshot to kill Master Hand, and leveled up from a Crook to a Gangster.