Please click on “Contact Support About this Issue” and submit the following essential information:

We require complete and accurate information in order to process your request.

Select 1024 x 768 or a higher resolution that is compatible with your monitor. My child forgot their password/username. If your child has forgotten their username or password, you can go to the Webkinz World homepage and click on the 'Forgot Login' button.

Required information:

-Username
-Adoption Code
-First Name of the User
-Date of Birth of the User (YYYY/MM/DD)
-The name of the pet most recently adopted on the account
-Desired Password

***As a reminder, any attempts to gain access to Webkinz World in a fraudulent manner, including but not limited to using fraudulent Adoption Codes or guessing Adoption Codes is grounds for the immediate termination of your account.***

This is straight out of the Poptropica FAQ website:

Q: I forgot my user name and/or password how can I retrieve it?

Forgot Webkinz Email

A: Unfortunately, if you've forgotten your username, there is no way to retrieve it. We do not store any private information about our users. We recommend you create a new avatar and write your username down on a piece of paper and keep it in a safe place!

Players can register a parent email address with Poptropica so that they can reset a child's password if it is forgotten. Your child must have input your email address through his/her player account and had the address verified specifically for this purpose before the 'forgot password' function will work. Please note that parents cannot change a player password through their parent account. To reset the password, begin by entering the username on the Returning Player login page, without entering any password, and then click the 'OK' button. Poptropica will display a 'forgot password' link. Click that 'forgot password' link, and then click the 'OK' button. Poptropica will send an email to the parent with instructions for creating a new password for the child's account.

Webkinz Account Recovery

I'm sorry to tell you, but unless you remember really hard or you put in an email, I don't think you can get it back. I know how frustrating that must be when you've completed so many islands and have a paid membership.

Webkinz I Forgot My Username On Facebook

Source: http://www.poptropica.com/Poptropica-FAQ.html#account.3