Toilet Duck was a toilet cleaning product made by SC Johnson in the mid- to late 90's. It got its hilarious name from the fact that the neck of the bottle was bent in such a way to make it resemble a duck's neck. This supposedly made it easier to spray Toilet Duck up under the lip of your toilet, thus removing mildew and other nastiness from it. You can see a picture of the bottle here:
What REALLY set Toilet Duck apart, however, was the advertising. The ads depicted a little fluffy duck-puppet thing, dressed as a World War II pilot, flying a bottle of Toilet Duck which had been modified to look like a fighter plane, with little wings and a single propeller. He is introduced with a military-sounding fanfare - "Dun da-da-dun DUN DUNN!" Cut to a profile of the duck pilot, who turns to the camera and quacks twice. He then proceeds to do battle with the mildew and other gunk that lives under the rim of the toilet. This was important, since the ads made it clear that the toilet sub-rim region is teeming with fatal diseases in the shape of evil lumps of green clay.
Sadly, it seems that consumers and homeowners were not as entertained by Toilet Duck as I was - it seems they have since stopped selling it, at least in New England.