''Invite friends to proceed''viral app script?

So I've seen FB fake game apps like play GTA vice city that have ''Invite locker'' that automatically selects a few dozen friends and asks to send them invites with a click of a button. When it's done, app proceeds to redirect. How is that done? Any script available for download/purchase?
Basically here is an example. https://www.facebook.com/appcenter/mygtavicecity
Please let me know asap

one of the most simple scripts out there.
just like any app, it gets deleted quick, unless you run it with lower number of friends to invite like 5
but then it wont really go viral which is why you dont see anyone running it

Thank yo, so where is it then and how is it called?