How do I get the hidden achievement in the new Google Play Games app?
From the main listing of games in the Google Play Games app, you need to swipe the old Konami Code:

↑ Up, ↑ Up, ↓ Down, ↓ Down, ← Left, → Right, ← Left, → Right (and then when the retro button grid pops up), B, A, ▶ Start.



You should then see an achievement notification pop up.



Here's a YouTube video that demonstrates how to do this.

via Android Central