Story for each variant

Berserk Mario (Based on Dorkly video; Mario Goes Berserk) - In this universe, Mario; after going through many hardships, finally snaps and kill his opponent, Bowser. Going on the full-on rampage on his own civilians and anyone who gets in his way.

Green Mario - In this universe, he and Luigi fought for their lives after a rumor spread throughout the Mushroom Kingdom of them having a virus and infecting the townsfolk, after fighting for days, Luigi was captured and killed, thus causing him to get his revenge against the civilians.

Imprison Mario - In this universe, Mario fought the Bowser and his koopalings a bit too early and was beaten very hardly, instead of killing him, Bowser had an idea to imprisoned him and forced feed him propaganda against the mushroom's creatures and forced him to kill them for "their wrongs".

Toad Mario - In this universe, Mario & his brother and the group of Toads, overthrows the Mushroom Kingdom and "freed the Toads", and since they "free them", they decided to wear their outfits out of respect of them.

Wood/Geno Mario - In this universe, Mario spilt apart from his team & his brother and followed the steps of Geno and Mallow into the forest. After spending years in the forest, he was discovered by Bowser & the koopalings and killed Geno and Mallow, as of result. Mario killed all of the koopalings and spared Bowser life & insisted Bowser to live with him.

Zombie Mario (Based on Mario Odyssey's outfit) - In this universe, Mario & Luigi when into a cave after hearing a cry & inspect someone was in there, crying for mercy. After Mario & his brother went in there, they didn't find anyone at all; till Luigi started to act strange, Mario was confused and asked his brother if he was okay. Luigi ran at Mario and bitten him, Mario in a state of shock, killed his brother. But since he got that nasty bite from him, it causes him to be infected and turn him into a zombie.

I probably gave them a bit too much detail, mb

~ So Retro ~