Like the delicious treats they’re named after, Easter Eggs found within Android have become a huge part of Google’s OS, the most popular of which is the version number secret. Just tap on the version number a few times, and after a special screen appears, in the right sequence and you’ll uncover a nice little secret that you might not have otherwise known was there. It’s not integral to the overall experience, but it’s fun for us geeks to feel like we’re a part of Google’s secret labs.

Google’s Nat & Lo went behind the scenes to talk to some of the company’s employees about why these Easter Eggs are even included in the first place. The first time a major Easter Egg appeared was in the Gingerbread release, which included a Zombie Gingerbread picture drawn by Jim Larson. It just kind of grew from there, culminating into the Flappy Bird-like game we saw hiding in Lollipop (and Marshmallow).

Check out the video above to learn a bit more about Easter Eggs.Oh, and by the way, Marshmallow is now available for older Nexus devices, and you can find the download links in this post.