Frequent younger shoppers to Starbucks know about the little secret called "The Secret Menu." The Secret Menu has all sorts of exciting flavors that you won't see on the main menu.
The key is you have to know all the items and ask the Barista if they have those items. As long as they have the items for the recipe, they will make it for you.
Sometimes they don't know the drink by it's Secret Menu name so it is best to order the drink by its custom name and then do the add-ons.
For example the Twix Frappuccino.
It's really a caramel frappucino with 2 pumps of hazelnut syrup, java chips, extra caramel and mocha drizzle.