I'm having similar problems.... with the missus. I've got her to say "Bell", "Twin Squirrel" and "Hughey" as they appear on TV.
Unfortunately, your son seems to be doing a lot better (if we ignore that he's now turning 'to the dark side'), as the missus tends to say the above in the same order until she gets the nod of approval from me...
I'm contemplating putting subliminal snaps of helicopters into her Eastenders videos to see if I can program her, but if that fails, its going to be the negative re-inforcement via the mains socket and her slippers...
What is it the Americans say - Can't Live with 'em, can't shoot 'em.