Here's how to do it:
Firstly, you'll see a message prompt from Rockhopper. He tells you to go to the Forest to check out his bot and help him take it down. Click "Go there!" and you will notice Rockhopper's MascBot going berserk.
Click the robot. RH will tell you to defeat the bot with a Pink Flamingo. Go to the Ice Rink to find it.
Pick up the flamingo from the goal to the right of the rink:
Click it and then return to the Forest. You have defeated the robot that was roaming Club Penguin! Everyone can pick up a Pink Flamingo hand item, and members can receive the Rockhopper bot head for free.