SMG4: If Mario was in... Deltarune is the fifty-sixth episode of Season 8 and the four hundred and sixty-fourth overall to be uploaded by SMG4.
This video is also the fourteenth episode of the If Mario was in... series. It also debuts several characters from Deltarune such as Susie and Lancer and is the last video of both Season 8 and 2018. It was aired on December 29, 2018.
Mario finds him in the world of Deltarune (or Undertale 2).
Mario is driving in his go-kart while reading a book on how to drive for dummies. In the process he ran over a stop sign, a man, and a taxi cab before noticing that he was heading straight into a barricaded tunnel. He made a quick turn right, leading him onto a rural, unpaved road. This unfortunately led to a steep cliff, causing Mario and his kart to fall into another tunnel that brought him into Hometown from Deltarune.
In Hometown, Mario started causing all sorts of chaos on his kart by running over some citizens, hitting a car, and even stealing a donut from Undyne (who dressed as a police officer), resulting in her and the police chasing him to a school. Realizing that he was now on the run, Mario broke into the school before Undyne could find him near his kart.
After entering the school, Mario decided to look for a way to escape Undyne but was forced to go the other way after seeing Baldi in the right-hand hallway. He entered a classroom and was subsequently accepted as a "foreign exchange student" by the teacher, who happened to be Alphys. Shortly after, Susie stormed into the room, at last "on time for once." However, Mario then proceeded to insult Susie by calling her "Barney" leading her to leave the classroom. He then called her a bitch, resulting in Alphys sending him out after her so he could apologize to her. In the hallway, Susie was about to beat Mario up but he managed to run away, even when Undyne had entered the school to give Mario payback for stealing her donut.
Eventually, Mario and Susie both entered a dark room where the door closed behind them. They both fell into the Dark World where Mario played with one of the local "objects" prior to stumbling upon Castle Town and the Fountain of Darkness (which Mario claimed was made of Pepsi). Excited about the presence of the fountain, Mario ran into the castle where a cloaked figure started telling him about a legend (albeit boring Mario to the point of him sleeping). The cloaked figure then encouraged Mario to join him and save the world, revealing himself to be a green guy with glasses named Ralsei. However, Mario refused to comply with him and kicked him away, causing some dark being with a spade logo to run into the Italian with a motorcycle. They passed by Susie, who was also disagreeing with Ralsei's intents for her, and looking at Ralsei's training dummy, which she did not like looking at; this caused her to want to join in on the action as well.
Later, the motorcycle-piloting figure stopped and revealed that Mario wanted to take the fountain from his kind. However, once Mario told him about the liquid coming out of the fountain, he also became excited about the fountain, causing the two to start fighting (the motorcycle being's name is revealed to be Lancer in the battle).
After Mario unleashed his "inner demons", the fight was interrupted by Susie who destroyed the "demon" with an ax. She declared that she was joining the fight due to still being pissed about what Mario did earlier, only for Ralsei to resolve the conflict by singing (albeit horribly, which fried Mario's head and set Susie and Lancer on fire).
Now with the conflict settled, Ralsei ordered the others to stop their quarreling and join him so they could "save the world". While walking towards the Card Castle (the location of the Eastern Fountain that was disrupting the balance between light and dark), the four encountered King Round blocking their way. Lancer explained that the checker patrolled the area as a defender of the fountain, causing Susie to take out her ax and prepare to fight it. However, Mario decided to give the beast a "Mario hat" and tame it, causing it to run into the heroes and rampage through the area. It kicked and stomped on various Darkners in the Dark World before jumping on top of the Card Castle. While doing so, the checker crushed Lancer's father (the King) and Rouxls Kaard (who cooks macaroni and cheese at the moment), smashed through several floors of the castle, and ended up in a room, where Jevil happened to be locked up for his view of the world. Not thrilled about what happened earlier, Susie tried to leave the room but the door here disappeared as well. Asking if the heroes were prepared for his "game", Jevil proceeded to turn everything in the room (except for Lancer) into their 3D forms (with Susie having a basis of Barney, a joke to what Mario called her earlier).
In his "game", Jevil fired some explosive energy balls while evading his challengers' attacks; he even used a dagger to stab Ralsei, who disagreed with his own beliefs. Mario asked Lancer to help, but all he did was cheer him on. However, when Jevil started taunting the others about being able to do anything, Mario immediately used those words to counter-attack his powers by questioning them, going as far as questioning if he could spawn dangerous lethal weapons at all. Not realizing that the heroes have exploited him to their advantage, Jevil proceeded to drop a series of miniguns, RPGs, and other explosive firearms on the battlefield.
Mario, Ralsei (who was under the impression that the weapons weren't lethal at all, and instead made anyone he shot his friend by Mario), and Susie (who commented that she liked her machine gun) then defeated Jevil using the guns he summoned. Lancer claimed they make a great team, but the others glare at him because he didn't do anything. The four then climbed out of the hole that they made with Round, with Ralsei thanking everyone for their efforts in "saving the world". While Lancer and Ralsei remained at the Card Castle, Susie and Mario left and made their way to a light portal to not only return to Hometown, but also seal off the Eastern Fountain to restore balance to the Dark World. They both woke up back at the school, presumably in the dark room that they entered earlier, now littered with all sorts of games and playing cards. The two said their goodbyes in the hallway as Mario headed out of the school, even though Susie still wanted her revenge on Mario for calling her "Barney".
As Mario exited the school, he realized he was surrounded by Undyne and the military in addition to her police forces, due to his 5-star wanted level for stealing her donut.
- Dr. Kleiner
- Purple Guy (Deltarune)
- Blue Ears
- Dad Cat
- Father Alvin
- Snail Guy
- Temmie (appears at 01:34)
- Monster Kid
- Training Dummy
- Seymour Skinner (Mario's "inner demons")
- Puzzle Guy
- Head Hathy
- Rouxls Kaard
- Barney (mentioned by Mario, used as Susie's base model in Jevil's game)
- Police force
- SMG4: If Mario was in... Baldi's Basics: Mario still fears Baldi as when he sees him in the right hallway he immediately runs to the left hallway and into Alphys' classroom.
- This is the first episode where Mario spends most of his time as his Deltarune form rather than his SM64 or GMod form.
- This video may be considered as a sequel to Mariotale - If Mario was in...Undertale..
- However, Mario doesn't seem to recognize Alphys or Undyne. This is likely a reference that Deltarune takes place in an alternate continuity from Undertale, possibly meaning that this episode takes in an alternate continuity itself.
- Sans appears in the YouTube thumbnail but not the video itself.
- This is the first episode of Mario's N64 model being used in the YouTube thumbnail since If Mario was in... Assassin's Creed Origins.
- Susie's GMod form in Jevil's "game" did use an actual Barney rag doll as a reference to her being called "Barney" by Mario.
- Mario's argument with Jevil about his powers uses the audio from The Cat in the Hat film.
- Additionally, when Jevil realizes he's screwed after seeing Mario, Ralsei, and Susie have their weapons aimed at him, he yells "SON OF A B*(*CH)-", also from The Cat in the Hat.
- When Mario entered the school, he broke through the front door and left a hole rather than opening it. However, when he later exited and saw Undyne with her police and the military, the door was still standing, completely undamaged from earlier.
- There was actual genocide in this video (ex. the various creatures and monsters being crushed by Mario's kart and Round; Jevil shot dead by the Lighteners using some guns), despite the fact that it is impossible to kill anybody in the actual game (even if the player attempts to do so), unlike Undertale, where there's a genocide route (though you'll get the bad ending if you take that route).
- This is the fourth season finale to not be a New Year's video, the first being Super Mario 64 Bloopers: The Lost Gems Part 3, the second being Super Mario 64 Bloopers: Befriend the End and the third being SM64 Bloopers: SECRET LIFE OF GOOMBAS.
- This is the first video since SMG4: If Mario Was In... Starfox (Starlink Battle For Atlas) to not include Meggy, Saiko, and Tari.
- None of the Deltarune exclusive characters have appeared in any other video after this one, possibly due to the conflicting canons with the Undertale characters.
- 01:40 - School; Deltarune
- 02:47 - Fight Against an Armed Boss; Super Mario RPG
- 03:36 - Empty Town (Castle Town); Deltarune
- 03:42 - Victory Fanfare; Final Fantasy
- 03:52 - Fallen Down; Undertale
- 04:00 - The Legend; Deltarune
- 04:06 - sans.; Undertale
- 04:14 - Kirby Dance (Kirby Victory Theme); Super Smash Bros. Brawl
- 04:19 - Danger Mystery; Undertale
- 04:42 - Lancer; Deltarune
- 05:03 - Rude Buster (Battle Theme); Deltarune
- 06:14 - Victory; Dr. Luigi
- 06:23 - Scarlet Forest; Deltarune
- 08:34 - THE WORLD REVOLVING; Deltarune
- 09:46 - Field of hopes and dreams; Deltarune
- 10:10 - Dating Start!; Undertale