SMG4: Mario's Prison Escape is the seventh episode of Season 9 and the four hundred and eighty-two overall to be uploaded by SMG4.
This episode was aired on March 2, 2019.
The episode begins at a prison, where Mario and Luigi were kept for an unknown crime they committed. As Mario tried to find a way to escape, Luigi begged to be let out, saying his "mushy face" won't survive jail.
After another failed escape attempt, the brothers met Swagmaster69696969696 and Chris, with the former mocking them and refusing to let them out (Swag also called Luigi less "thicc" than Mario). After Mario punched Swag in the balls in retribution, Swag instantly got angry and opened the cell door to engage the fat plumber in a fight. After getting annoyed, Chris then pointed out to Luigi that it was ironic that they both have to deal with mentally retarded people in their lives, with Luigi agreeing.
At lunchtime, the Mario Bros. found the other prisoners doing their hobbies (and John Cena watching TV). Taking advantage of their idiocy, Mario attempted to escape by climbing over the fence, only to be shot by Swag wielding a rocket launcher. Despite Chris' protests, Swag proceeded to shoot Mario again, setting the plumber on fire, much to Luigi's dismay.
The brothers then discovered Fishy Boopkins (who also was arrested for no reason) saying that he and Bob (who was exercising in order to look badass, only to be ruined by Mario) came up with a plan to escape jail, though Bob wanted to use Mario as cannon fodder. First, the brothers poison the food with a Poison Mushroom, thus causing everybody who ate the food to throw up and start running to the bathroom. During the chaos, Bob, the Mario Bros. and Boopkins escaped through the air vent while Swag, Chris and some other guards tried to calm everyone down. However, Mario was a little too big for the vent and got stuck, revealing the plan to the guards. With no other choice, Chris gave Swag permission to kill them, which Swag agreed while carrying what seemed to be a giant-spiked hammer-pickaxe hybrid, ready to "banish some scrubs from existence".
Meanwhile, Mario told Boopkins (who was at the front) to speed up, as he didn't want to look at Bob's butt any longer, which in turn, caused Bob to taunt him. Suddenly, the vent started shaking, but Mario didn't notice the danger until Swag ripped a hole in the vent with the giant weapon right next to him, causing everybody to run. When Swag started to catch up, Mario proceeded to eat the poisoned soup as he remembered that he still had the food in hand and naturally vomit as a result, thus pushing everybody out of the air vent and the prison, with Meggy , Tari and Saiko waiting outside. After Boopkins revealed that he had called them for help, the males got in the back of the truck, with Meggy (carrying an unconscious Mario) joining in. However, Swag declared that he will not let them escape under his watch.
Grabbing a car offscreen, Chris chased them with Swag at the top carrying a rocket launcher with them (during the chase, Swag freaked out at Saiko's presence and wanted to kill her). After many failed attempts at trying to get them off their trail, the gang got shot down by missiles, causing the truck to stop. Boopkins tried to get them to stop, which didn't work. As they were about to be shot down by another missile, Mario woke up, and hallucinating the missile to be the poisoned soup he ate earlier, used Boopkins to throw the missile back at Chris and Swag, blowing them up.
The gang then started to question why Mario, Bob, Luigi, and Boopkins were arrested in the first place, and Mario flashed back. Apparently, Mario ran over a pedestrian with his kart, and tried to put the blame on Luigi and the others. While the police believed his lie, they arrested him along with everyone else anyway. The episode then ends with Mario lying that they might never know.