You should be able to. If you visit the Account Details page at https://aliensoup.com/account/account-details you should see a "Change" button next to your current user name. Click that and you can change your display name to something else.
Note that there are restrictions on how often the name can be changed so don't experiment, else you'll be stuck with that name for the next month or so.
Taking a look, if an email 'bounces', meaning it tried sending you an email and an error was sent back, after so many bounced emails the site restricts the account until the account is updated with a valid email. If you haven't already, you could try re-using your existing email assuming that the bounces were just a temporary issue.