Mario sets out to go buy the new 3ds but when he goes off course he's in another adventure
Mario was wondering where his kart was so he could go buy the 3DS before it was sold out, however, he didn't find it so he had to take the old kart as recommended by Toad, and he went left where was an incompleted bridge. Mario uses the levitate button to try to get across, but when he lets go of it it gets jammed, so he keeps levitating. After some time, the levitate button unjammed itself and Mario ended up in a "Gay Road" (Rainbow Road) and he races on it for a bit, falling out of it moments later due to getting scared at Luigi's face.
After falling through the sky, the Star Spirits find Mario and call him a murderer, so they fill his body with shame. A Goomba then finds Mario and thinks he is Luigi, wanting to cook him and runs off as Mario then wakes up and sees a bridge which leads to a cave.
He then explores it and finds a passage which leads to a "Swimming Pool", when he enters it he gets naked and became metal. He finds a waterfall and wants to see where it leads. When he gets to the waterfall, Mario somehow gets on his kart, and on a beach.
He goes through the sewers to get to town to where the shopping mall is. When he finally got to the shop, the 3DS was already sold out. Luigi took the last one, so Mario went to his house and wanted the 3DS off Luigi. Mario and Luigi then had a fight. Luigi won, but Mario stole it, who then ran away and went to the castle. Luigi followed and then punched Mario.