This is a true story
(or at least, repeated enough times to be true in Vancouver, WA
Apparently, the McDonalds on Mill Plain was the center of a drug smuggling ring in Clark County. The manager and some of the drive thru staff had setup a system whereby a buyer or distributor would ask for a 'special' to whatever meal they were ordering. The code worked, apparently for quite some time (since no one would order a 'Happy Meal Special'). Oh, yes, and a 'Happy Meal Special' would get you marijuana. Very happy, indeed.