Or just keep a list of all their seasonal items and just roll into ordering those:
Oh, ok, I'll have a mcrib. No?
Oh, ok, I'll have a pumpkin spice shake. No?
Oh, ok, I'll have a candy cane shake. No?
Oh, ok, I'll have the brontosaurus nuggets. No?
Oh, ok, I'll have the pluto is a planet burger.