That was when they got rid of the "blob emoji" in favor of adopting the more standard round smiley faces in order to match Apple specifically. The reasoning was along the lines of wanting emoji to convey the same thing across platforms, which makes sense to an extent but I'm not sure why they felt a complete overhaul of the artstyle was necessary to achieve that goal.
Also, the Google Noto Emoji's android uses are open source, so if you're looking for them you'll find them used in lots of logos. Super Auto Pets uses them for a ton of the icons and animals.