One year later challenges that can take place over one party

I'm throwing a party soon, and I want to make it based on the one-year-later challenge. I don't want to ask my friends to have to do anything before the party, so I'm sorta looking for ideas for them to do at the party. Preferably under everyone's noses. they'd present what they've completed at the end of the night

if anyone has any fun ideas, send them my way!!