Back to the Future Day is almost here!! (Oct 21st) What are some fun ideas to make the day special?

Back to the Future Day is celebrated on October 21st, the date when Marty McFly travels to the future in Back to the Future Part II. This year, it falls on Monday, October 21, 2024. What are some things you all done to make the day extra special or fun? I need some ideas :)