Next to the Pong machine at Gamescom 2019, there was a Pong Doubles machine with 4 paddle controllers. I played against a some kids, and quickly decided to play with two paddle controllers. This game is a lot of fun, and the double paddles adds a bit of depth to the game that the original didn't have - for instance, you can shoot the ball with the back paddle, through the front one, adding spin to the ball, which works as a nice feint. I won a few games against some kids, and one of them asked me if I was the original creator of Pong. I had to disappoint them there...
This version of the game had colored paddles. This was an interesting modification of the original hardware by Wolfgang N, which can be seen in this video.