Alastor 'Mad-Eye' Moody: Potter, you're underage. Which means you still have the trace on you.
Harry Potter: What's the trace?
Alastor 'Mad-Eye' Moody: If you sneeze, the Ministry will know who wipes your nose. Point is we'll have to use those means of transport the trace can't detect. Brooms, thestrals, anf the like. We'll go in pairs, that way if anyones out there waiting for us, and I reckon there will be, they won't know which Harry Potter is the real one.
Harry Potter: The real one?
Alastor 'Mad-Eye' Moody: [Brings out Polyjuice potion] I believe you're familiar with this particular brew.
Harry Potter: No, absolutely not.
Hermione Granger: Told you he'd take it well.