It was a beautiful day in the mushroom kingdom, there was a lot of flowers and nice weather out, everyone was having a lovely time outside except for two inhabitants.
That day, Mario and Luigi were at home, mario had gotten sick the morning before and it was unknown what was causing his problem. Luigi had the idea to go inside Marios body to see what was happening. He had a machine built which allowed him to go inside Mario. However getting the settings set took a while.
When luigi found the settings he set the machine to search for six hours to see if he would find the source of marios problem, the first place he looked was marios head, nothing concerning in the head area. He was there for about 5 minutes and he got the all clear to go to the next area.
The next area was Marios lungs, once again, nothing too concerning in the first area of the lungs, although he did find some scratches in one of the areas later, which made him think there was some kind of virus there.
The next area was Marios blood system. Everything was perfectly clear there, whatever was causing the problem hadn't appeared there yet. That was good news for luigi, however it was still unknown where the problem was.
Next area was marios vocal cords and diaphraghm, before luigi could get in there, he was trapped in by whatever was attacking Mario. Suddenly he found the source of the problem, apparently mario had the problem for over a day since it was spreading there. After finding the source of the problem, luigi went back to the portal and warped back.
Ten minutes later, Mario woke up and noticed luigi had been sweaty, Mario asked if luigi was okay, Luigi said i may have to get you to a doctor soon, it appeared to him whatever the problem was lasted a few days and he wanted to make sure it got treated. Mario didn't object and next thing he knew he was back asleep.