Who Wants Some Pie?

Do you mean a hundred, or one hundred? Surely if using the numerical 100, the "a" becomes superfluous.
The Henderson's Relish factory continually irks me for this very reason...

I really hate it when people talk of "the hoi poloi". Why "the" when one has the "hoi" immediately after. "The the people". Rather silly and demonstrates a singular lack of a decent classical education.