I originally made my Facebook account in 2007 to play a Flash game called Jet Man, which was basically Flappy Bird before Flappy Bird (I want to say the original famous version of this game both were ripping off was called Helicopter Game though?)
You would invite friends to play the game to unlock more characters, including copyright violating ones such as Super Mario, so I assume the game was removed from Facebook long before the death of Flash.
That game, and some mafia game, was what got our whole class to sign up in 2009 or so. Or, rather, if you didn't sign up someone made an account for you, so they could claim the benefits, hehe.
You would invite friends to play the game to unlock more characters, including copyright violating ones such as Super Mario, so I assume the game was removed from Facebook long before the death of Flash.