If you met Rookie online and got his stamp but not his background (due to errors etc.) email support@clubpenguin.com. Include that you met Rookie along with your username. If you really did, this is the reply you should get.
Hello,
Thanks for your email, I understand you met Rookie online today! As you have the stamp for meeting Rookie today, I was able to make sure that you received the background that Rookie was giving away. We hope you’re enjoying the Underwater Expedition!
If you have any other questions or difficulties please don’t hesitate to let us know, we’re always glad to hear from penguins like you!
Waddle On,
Sara,
<><><>Club Penguin Support<><><><><><><><><><><><><><><><><><<>
(Credit to Messi4ever55)
Comment and let us know if this helped you, we’d be happy to hear from you!
~ Jammer Dj
I knew that all along bro
I sent an e-mail like that at the halloween party, due to the error I couldn’t get Aunt Arctic’s background neither add her. So CP emailed me I couldn’t add her, but they could give me the bg, so they did. Then I re-added her at the Holiday Party again 
-Bastian7777
i have never ever met a famous penguin not once (unless you count billybob cos i have met him AND IT WAS SOOO EPIC!)
——-heh heh kisssy kissy
Cool post. Intersting!
WHERE’S ROOKIE??????
hey penguins ! i will be online on 4 february at the server ice pond and to the gift shop! meet you ther my secret agents.
I did that cheat it worked thanks cheats
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ok