Board Thread:Help Desk/Hay Day Wiki/@comment-24896668-20140504205738/@comment-5965519-20150517172314

Game Center is a function within the Apple OS. For those using iPhone or an iPad, they can go to their settings and sign in to the Game Center and create a username there. Then there is an app (included with the operating system) called Game Center. As you open that, you can see a category called Friends. You can click the plus sign + in that tab and write in the unique game center name of people you see in the game. An invitation is then sent to them, via their own game center interface, and they have the option to accept or decline your invitation.

Game Center can accomodate up to 500 friends in this manner. The names you see here in the Wiki in the Friend Requst  listing are people who are looking for additional game center friends.

I don't use Google play, so I will let others speak to whether or not the Google Play Services app works in a similar manner.