The crazies thing happened during my recent trip to New Donk City in the Metro Kingdom, a Giant Mario appeared out of no where. He didn't seem like he was trying to hurt people, in fact he was quite careful not to.
Understandably the people were in a panic, and so the army was called in.
General Mario; "Alright giant, state your intentions!"
Giant Mario; "I'm not a giant, at least I didn't want to be. I was just an ordinary Mario an hour ago."
The Giant Mario explained that he was out for a walk when a mysterious Mario gave him a mushroom and after eating said mushroom grew into a Giant Mario.
Since the Giant Mario wasn't causing any problems since he appeared, General Mario decided he would have his army help the Giant Mario and get him out of the city to a place where he and other's would be safe.
Giant Mario was soon relocated to the Cascade Kingdom where no one would get harmed until Giant Mario can be returned to normal.
As for the mysterious Mario who gave him the mushroom, his whereabouts are currently unknown. An artist rendering has been distributed all around the Metro Kingdom.