Don't mind me, back at it again with the East/Southeast Asia-related suggestions
Mid-Autumn Festival is a very popular and important festival, on par with Lunar New Year for countries that celebrate both.
Some other ideas: Dragon Boat Festival, Songkran, Holi, Diwali
Also, others have brought up Talk Like a Pirate Day and I want to see that as a mini-event so bad!
Edit: Also, a World Teacher's Day? Globally it's held on October 5th and I could see so many adorable pets: a chicken surrounded by chicks running around and squawking, a dog with glasses with a chalkboard behind them, maybe some references to more culture-specific teachers like how teachers are more revered in China, Korea, Japan and Vietnam with regards to Confucianism and college professors.