How do I get the unicorn or dragon frap?

I'm reading about the new unicorn and dragon fraps, and how it's on their secret menu. I didn't even realize they had a secret menu, but apparently it's so popular that they're running out of ingredients to make them.

Is this something I can just go up to any starbucks counter and ask for? Or is this only in participating locations? If the latter, which locations offer these new drinks?

So confused.