Android 7.0 Nougat allows users to access older easter eggs from previous software versions, specifically those which can be found inside of Android 6.0 Marshmallow and Android 4.4 KitKat. These are in addition to the cat catching game that comes along with Android 7.0 Nougat, which means that users can access all three if they so choose, although it is worth mentioning that getting to the two older easter eggs is not as simple and straightforward as opening up the official easter egg for Android 7.0 Nougat which is accessed via the standard method of tapping on Android version from the about phone menu in settings multiple times.
If you still enjoy the Flappy Bird craze, or Flappy Droid as it's essentially known in its Android easter egg counterpart, accessing it is still a mostly easy task and doesn't require much more effort on the part of the user than getting to the official Android 7.0 easter egg. It's possible to open it up through the means of launching an activity, which can be done in a few different ways including using an app that's dedicated to helping users launch system activities, such as Activity Launcher, or by launching an activity through the means of an actual home launcher like Nova or a few others where activities are accessible via shortcuts.
Once you've chosen your method, scrolling through the list of activities and coming up to SystemUI, then expanding that list to reveal activities specific to that category can lead you to an activity called Marshmallow Land, which you may be able to guess is the Android 6.0 easter egg that featured a white colored Android that you could manipulate as you tap the screen, all the while dodging Marshmallow shaped obstacles to get a higher score. Getting to the Android 4.4 KitKat easter egg is achieved through the same method of launching an activity under the SystemUI list, and you'll be looking for the name Dessert Case. While the Marshmallow Land activity allows users to open up and play the Flappy Droid game, initially opening up the Dessert Case activity and launching the KitKat easter egg will unlock Dessert Case as a screen saver option moving forward.