Super Mario Bros. Fungi Outbreak is a CGI animated Comedy/Action film based on the Mario franchise. The film was released in 2017 but the project was leaked two years before the release of the film via a leaked eMail conversation between Nintendo and Sony.
The film starts with a view of the Mushroom Kingdom as it travels through many familiar places until landing on Bowser riding his Klown Kar all the way to a village where the villagers run in fear, all except Mario, Luigi and two Toads: The blue toad "Umi" and the yellow Toad "Kin". Mario and Luigi are preparing food so they don't notice Bowser until he crashes through the wall, they all start throwing things at Bowser but he blocks the hits and closes in on Mario until revealing the reason he's there: He needs Mario's help to fix a problem in his kingdom which he says was caused by the current ruler of the Mushroom Kingdom, "Peach Toadstool VII".
Mario, Luigi, Umi and Kin go to Bowser's kingdom where Bowser tells them to be careful and cowers in fear when they see a Goomba, who looks completely normal until a mushroom grows on its head and it becomes a zombie mushroom monster. Mario, Luigi, the two Toads and Bowser examine the Goomba and track down the source of the fungi all the way to the Mushroom Kingdom, with Princess Peach ending up as the main suspect. In the end, Peach is arrested even though she insists she's innocent and she starts crying in her cell until noticing the Toad Guards have also turned into mushroom monsters.
Peach calls Mario and Luigi who free her and they examine the Goomba one more time and this time they find that the source is Rogueport. The gang builds a boat and sails all the way to Rogueport and walk around the bay with disguises until the disguises fall off and the police chase them, thinking that Peach is the culprit. The ganag manages to escape and hide in Prof. Frankley's library where they try to get Goombella's help on finding the true culprit until noticing that the Goomba they brought with them has been stolen by some bandits.
The gang chases down the bandits while going into hiding and confront them only to find that they've all lost the Goomba, the gang runs outside in a panic and finds that most citizens of Rogueport have now turned into mushroom zombies. The gang battles through the horde, get the Goomba and go back to Frankley's library where they examine the Goomba once more and find out that the mushroom has DNA from all over the world, with nowhere to go the gang wonders what to do until a mysterious man under the name of "Vegette" who knows alot about plants checks out the Goomba and tells the gang more about the fungi.
Apparently the fungi is a fungi that Mario and Luigi accidentally brought from Earth when they went to the Mushroom Kingdom for the first time, when the fungi suddenly landed in the Mushroom Kingdom, it reacted strangely to the new land and evolved. The fungi is linked to other fungi throughout the world via a set of underground tunnels and roots, thus explaining the strange DNA results. The gang decides to go to this underground tunnel and take down the core, but first they must find a place where they can access the tunnels.
Bowser thinks the place should be around the forest near Rogueport but Peach thinks that Bowser wants to lure the gang into a trap, they argue for a minute until being interrupted by Kin who asks why Bowser and Peach hate each other so much. Peach reveals that their ancestors have been at war due to territory problems for years until many years ago, Bowser Koopa IV offered to end it all with a forced marriage between the two, however "Peach Toadstool IV" was disgusted at the idea and denied it, and since then the Koopa line has been trying to force the Toadstool line into marriage so that the Mushroom Kingdom's territory can be their's.
The gang finally ends up trusting Bowser and find a tribe of Yoshis who tell them that there is a way they can admire the tunnels, however when the gang reveals they're planning on ending the fungi, they suddenly grow hostile, since the fungi has been there since a long time ago and they think of it as a sacred relic. The gang have no choice but to fight the Yoshi tribe, which they do before entering through the tunnels.
While walking through the tunnels the gang finds a swarm of mushroom zombies but manage to hide, in the process Kin realizes he and Umi may become zombies as well, Umi calms him down and assures him they're not gonna turn into zombies shrtly before turning into a zombie himself, forcing the rest of the gang to fight Umi and Kin. The gang manage to capture the two in some cages before being swarmed by the same mushroom zombies from before.
The gang try to flee but notice they're caved in, so they fight off the zombies until Mario resorts to throwing things until finding a Fire Flower plant which actually reverts a Goomba back to normal until being infected again shortly after. The gang uses the Fire Flower on Umi and Kin which reverts them back to normal and they continue their journey until finding the core of the fungi, which has taken a humanoid form as a monster named, "Cepicordya", who thinks of herself as the queen of the zombie fungi.
The gang then have a showdown against the army of fungi zombies until Mario and Bowser finally team up and defeat Cepicordya, however, after her death the tunnels start crumbling down, so the gang escapes the tunnels and use the Fire Flower plants on the citizens of Rogueport to turn them back to normal. After that, they try to think of a way to spread the fire power throughout the world beofre being interrupted by a zombified E. Gadd, they turn him back to normal and he explains he was working on a rocket, which the gang eventually uses to spread the Fire Flower's fire power throughout the whole world and save everyone.
After that, Mario wants to get back home since he's tired and wants to rest, everyone else agrees that they need to rest, even Bowser, but before they leave Mario and Bowser shake hands and promise to go back to being rivals soon enough.