There's a room on StackOverflow in Russian where you can see such an interesting discussion:
Just because there are not enough real discussing in that room, @Grundy "plays ping-pong" to keep it unfrozen.
Implement a bot for StackExchange that posts "ping!" to the 115624 room if the previous message was "pong!" **(and posted by another user) and "pong!" if the previous message was "ping!" (and posted by another user).
If you need a login and a password for SE account, use
**It should not reply to its own messages
Code-golf: the shortest answer wins.