Long story short, Toga and Twice had let in some rando from the streets to stay over. The rando was a squatter and thief looking for shelter from the rain. Though he didnt dare steal anything from the League Of Villains that night.
He'd offered to grant everyone one wish, as it was his quirk. Someone could ask for a wish, he'd grant it, and it would happen the next day.
Once it was Tomuras turn, Tomura blatantly refused to make a wish, not wanting to seem like an idiot the next day when nothing happened. Too bad the guy liked to snoop around, and for some reason really wanted to show his gratitude. He somehow got into Tomuras room, did some searching and found out Tomura had a favourite video game character. He granted a random wish on Tomuras behalf; the character would no longer be fictional, instead appearing in Tomuras room the next day.
By the time dawn rolled around, the invasive and mysterious squatter had left the Leagues hideout without a trace. Awhile Tomura was confused and freaked out when he woke up to his favourite video game character that he mained so much, standing right in the middle of the room, looking terrified and as confused as him.