MacRumors has uncovered a sweet new feature in watchOS 4. On your birthday, the Apple Watch will wish you a Happy Birthday and send balloons floating up your screen.
This balloon animation is similar to the balloons message effect in iOS 10. Granted, this is a small feature in the scheme of things, and not something that would be spotlighted at WWDC. But it is one of the delightful surprises that so many of us love about Apple products.