SMG4: The Mario Mafia is the eighth episode of Season 8 and the TBA overall to be uploaded by SMG4.
This episode was aired on February 24, 2018.
The video starts with Toad carrying a person in a garbage bag into a building. Once they reached the hall, Toad removed the bag, revealing the person to be a Goomba. He then ordered the Goomba to go across the hall, who met Steve, Po, Bob Bobowski, Fishy Boopkins, and Luigi, who were all guarding the hall.
The Goomba eventually reached the door to see the don, revealed to be Mario with his subordinate, Meggy beside him. Mario wanted to know why did the Goomba did what he did: splatting his plate of spaghetti. He also mentioned how he knew who did it: In this case, it was because Mario spotted the Goomba outside his house. He then made an organization called "Mario's Super Awesome Mega Mafia Group". There was a brief argument from Luigi and Meggy about the name before Bob joined in, asking when would they be paid. This only caused Mario to tell him to shut up before threatening the Goomba that by the count of three, he would reveal his boss lest he would be attacked with a baseball bat. Feeling horrified, the Goomba revealed the boss to be Bowser due to him not being invited to Mario's party. That caused Mario to get revenge on Bowser.
At a beach, Bowser, Bowser Jr., and the Koopalings were relaxing, Bowser Jr. asked his father if what they did to Mario was too extreme. However, Bowser didn't care and thought Mario deserved it, then Lemmy Koopa reported that his clown car was being vandalized. Bowser went to check on it and saw Mario spraying graffiti on it, with the sprayed words saying: "Pingas". Feeling angered naturally, Bowser ordered Bowser. Jr. and the Koopalings to open fire on Mario, forcing him to escape.
Since Mario got away, Bowser decided to call someone to get his revenge on Mario. Meanwhile back at Mario's base, Mario was boasting the feat of his revenge on Bowser, where everyone except Meggy laughed at the outcome. Suddenly, there was a gun being fired at them. Turned out it was Bowser who used two miniguns to do so. As he wondered how he found out, it turned out that earlier, Bowser past by a sign that said "NOT Mario's Sexy Base" and decided to shoot at it anyway. When he was done firing his guns, he told them to get fucked before leaving. Mario and his gang then realized that someone in their team has been ratting them out.
Mario determined to find the culprit and inspect all of the members of his group. Po was first and was thrown out of Mario's office after. When he inspected Luigi, he freaked out because he had a rocket launcher pointed at him and Mario pulled his face, wondering if Luigi was wearing a mask. When he inspected Toad, he tortured him with his girlfriend Toadette on a leash. Suddenly hungry, he accidentally let go, causing Toadette to rip apart Toad. When he inspected Fishy Boopkins, he threatened to shoot his anime DVD collection with his gun if he didn't tell, but Boopkins threw himself and his box of anime out of the window. When he inspected Meggy, he tried to speak her language so she could understand him, only to get hit by a chair.
Just when Mario was about to give up, Bob who was out of the scene came, and everybody looked at him, so Bob said he was going to shit outside and went out through a window. The gang followed him, and it was revealed that Bob was working for Bowser to get money, but Bowser gave him fake monopoly money. When Bowser escaped, Mario and friends captured Bob with Mario threatening him that he would remove his balls if he did not tell them where Bowser's base was. Bob did not care if they chopped off his balls, so Mario took him to a prison cell to watch Fishy Boopkins play Roblox for 10 hours. Rather than suffer from that, Bob revealed Bowser's location.
Then they headed to the hotel with Bowser dancing in his hotel room on the top floor listening to headphone music at maximum volume, with Bowser Jr. and the Koopalings keeping watch in the lobby. Steve then walked in wearing a maid outfit and pushing a towel cart, claiming to be housekeeping. After Bowser Jr. told him to leave, he shouted "INCOMING" and ran away. This was Toad's signal to jump out of Steve's towel cart and start firing. Meggy, Mario, and Luigi then fell through the windows on the ceiling, but Luigi landed on his face. After they stopped panicking, the Koopalings fired back, causing them to hide behind a pillar. Wendy then ran out of the lobby screaming for her father, which caused Meggy to chase her. Mario then asked Steve for backup, who then killed the remaining Koopalings.
Meggy was able to catch up to Wendy before she reached Bowser and they had a stand-off, with Meggy repeatedly shooting Wendy's weapons out of her hands. This angered her and caused her to rush at Meggy, who simply tripped her and kicked her out a window.
Mario, Luigi, Toad, Meggy, and Steve then broke into Bowser's hotel room and Mario knew that Bowser has touched Mario's spaghetti. However, Bowser apologized to Mario for doing that after not being invited to Mario's party. Mario said he didn’t give a shit, so Bowser said he would now buy Mario as many spaghetti as he wants. Mario said it was the nicest thing someone has ever said to him, so they hugged. Toad and Luigi just left and Steve was crying as well. Meggy asked if they were finished but only saw them all crying. She then also left with Luigi and Toad, leaving Mario, Steve, and Bowser crying.