SMG4: Mario Raids Area 51 is the twenty-eigth episode of Season 9 and the five hundred and thirteenth overall to be uploaded by SMG4.
This episode was aired on July 27, 2019.
Mario makes a new friend and he's taken to Area 51... Nothing else to do but Naruto run in and raid it I guess.
The video starts with Mario, Luigi, Meggy Spletzer, SMG4, and Saiko on a local beach when a UFO crashed-landed nearby. Mario goes off to inspect it out of curiosity, however when an alien stepped out of it Mario automatically proclaimed him his "best friend", dubbing him Greg. However, the Mushroom Kingdom army quickly arrived and abducted Greg, but a general accidentally revealed the location where they were taking the alien to: Area 51. Attempting to cover it up, the general ordered that Mario had his memory erased, however, when Mario started to annoy the soldiers they instead knocked him unconscious.
When Mario woke up, he went off to Area 51 to rescue his alien buddy.
Later, Mario arrived at Area 64, mistaking it as Area 51. One of the Squirrel Soldiers were nice enough to give directions to Mario, which Area 51 was surprisingly next to Area 64. His first attempt is to beg one of the guards to release Greg, which failed horribly. His second attempt is to climb the walls of Area 51, which it backfired horribly, due to one of the guards (who looks like Thomas the Dank Engine from SMG4: Mario's Train Trip) shooting him on fire. His third attempt is to fly to Area 51, which failed horribly due to the guards shooting the flying plumber. His last attempt is to dig around the dirt, which he meets SMG3, who asked Mario to get his own tunnel to Area 51 before kicking him out.
Just as Mario was out of ideas, the "Boy Scouts" Bus appeared, introducing Shroomy, and his boy scouts. Mario got the idea to pretend to be part of the group. He disposed of a Monty Mole called Jimmy and took his place, playing off as just being bigger from before. As the group toured Area 51, Mario wondered where Greg was. The moment the group was occupied with the gift shop, Mario went off trying to find Greg. Going through the area, he did manage to find Greg but a guard spotted him. Mario claimed he was the cleaner, causing the guard to ask him to clean sector 2. Mario, being dumb, gave away the truth by claiming he was not going to clean that sector. Naturally, a whole squad surrounded him and tried to arrest him.
As Mario evaded the soldiers, he resorted to releasing all the aliens with his "hacking" skill. It worked but now Mario also had to deal with the freed aliens. Grid Xenomorph tries to attack Mario and Greg. Fortunately, Mario shoots it with gun. Grabbing Greg, he ran away as quick as he could. Now back at the gift shop, Mario asked Shroomy (who somehow did not recognize him earlier) to help repel the guards and aliens. Shroomy agreed, saying that he and the two other scouts were trained in extreme warfare. As Shroomy prepared a nuke to wipe out Area 51, he told the two scouts and Mario to delay the enemies. It worked and the group barely escaped, with the two scouts now burning. Mario then celebrated with Greg, who finally showed an expression of joy.