Dr. Pinguis Thinning Elixir

Dr. Pinguis Thinning Elixir was a weight-loss potion manufactured by the company Rhubarb & Thistle. An advertisement for this product appeared on the Knight Bus in 1993, promising to "banish flab forever!" and "magic the pounds away!", or else refund the purchaser's sickles.

Etymology
Pinguis is a Latin term with several meanings, including "fat, plump" and "dull, stupid, obtuse." This may have been intended to suggest that usesr of the Elixir are likely to not only be overweight, but silly, in that they are gullible enough to be convinced into buying what is most likely an ineffective snake-oil product.

Appearances

 * Harry Potter and the Prisoner of Azkaban (film)