twitter help please!?

[lala]

so im following sprinkles cupcakes and they give tweets saying you have to whisper" ____" in order to get a free cupcake.
so how do you whisper on twitter. i don't get it!
so here is an example.

You asked and we listened! The first 50 people to whisper “fan's choice” get a free strawberry cupcake! about 10 hours ago via web

so any ideas what that means!?
thanks.

[john]

It's a joke, ha ha