Along with the new Minnie Mouse Watch Face in watchOS 3, Apple has also snuck in the ability to have both Mickey and Minnie actually announce the time when you tap on them.
The feature is normally enabled by default for both of these Mickey and Minnie Watch Faces, but if you’re having trouble, swipe up to access Control Center and make sure your watch isn’t set to silent mode, and go into the watchOS Settings app, choose Sound & Haptics, and scroll down to ensure that Tap to Speak Time is enabled. If it’s the first time you’ve used the feature, you may also need to ensure that you’re connected to Wi-Fi (via your paired iPhone) and wait a few minutes for the necessary voice data to be downloaded over the Internet.