[It's a certain someone's birthday - not that he's told anybody - but instead of celebrating it, he's decided there's an opportunity to celebrate everyone! Once the rain has let up, at least a little, there's a giant message-board near the new houses. It seems to have everyone's names on it, and above is written -
HAVE A VERY MERRY UNBIRTHDAY, EVERYONE!
"What's an Unbirthday? Why, that's a day that's not your birthday! You deserve a chance to celebrate yourself, because you're amazing! And if you think someone else is amazing, be sure to let them know!"
With all the pens and markets waiting at the bottom, it seems to indicate that you're encouraged to write compliments under people's names. Try to be anonymous? Get caught in the act? Only compliment yourself? Give it a try!]