Eh actually, I have it on a good authority that the REAL start of that spell is hubble bubble toil and trouble Kat.
Now if, and this is purely speculation on my part, one required to be unseen then why, if one has a knowledge of the Kraft, would one require a smoke screen!!!? Most folks in the 'know' say like 'Professional Crafters'   would mearly use the spell that begins with....muggles,fumbles, embroils and baffels...ect
As you can see I did subscribe to Sinsull's link and the things I have learned today are frankly mind blowingly wow. So needless to say...I now am in possesion of 'THE Secret'.
Money well spent I can tell you.

Cackle, hackle, horse and mackerel
J