Dyngus Day is a Polish-American day-after-Easter tradition celebrating the end of Lent. It features people playfully sprinkling each other with water and swatting one another with pussy willows to show their amorous interest.
Through a protracted fit of laughter last year, Cooper said, "It's so stupid, really so stupid." He later said he was referring to his giggling, not the holiday.
Organizers set up a website to try to persuade Cooper to attend and offered to name him the festival's first pussy willow prince.
But Cooper tweeted Thursday he's "really sad" he won't be able to. He says it sounds like "a lot of fun."