Does your Penguin name currently show as "P" followed by a series of numbers? For example, P123456. If so, this indicates that your username has not been approved yet.
Penguin name verification is done manually by the Club Penguin Legacy Team. Therefore, it could potentially take up to approximately 3 days for it to be approved.
If you find that your username has not been approved within 3 days and you believe it is appropriate to use, please contact us by creating a support request here. When contacting Support in this scenario, select the issue as "Security Support" and the "What do you need help with?" option as "Appeal Username Approval". This way we can manually approve it for you or provide an explanation in the case it was deemed inappropriate for use.
