You can play as Luigi in Super Mario Bros. 35
Luigi is actually a playable character in Super Mario Bros. 35.
Super Mario Bros. 35, Nintendo's take on the battle royale genre with Mario's platforming fundamentals, has been popular with players since its release. When the game was announced, Nintendo only showed it off with Mario as the playable character.
Now, however, players have discovered that Luigi is hidden within Super Mario Bros. 35, and you can even play as him. As reported by Eurogamer, the community came together to try and figure out Luigi's unlock requirements.
After some digging, players came to the conclusion that you need to complete every stage in the game at least once if you want to play as Luigi. Once you've done that, all that's left to do is hold L when loading into a match and your character will change from Mario to Luigi after the countdown.
@CombotronRobot on Twitter pointed out that you need to keep holding L while you select the stage, just like you would in Super Smash Bros. Melee to flip through alternate stage music.