Noggenfogger Elixir is a consumable, available after completing the Neutral Noggenfogger Elixir quest from Marin Noggenfogger in Gadgetzan. It turns you into a skeleton, can make your character small and/or add a Slow-Fall effect. The different effects will stack if you consume multiple Noggenfoggers, so you can be, for example, a tiny skeleton.
From patch 2.0.1 to 2.3.0 Noggenfoggers were on a 2 minute cooldown. It was removed, as well as the global cooldown, allowing players to repeatedly use the Noggenfogger until they get their desired buff.
Background - This dark green substance resembles an oil at first glance. It is so thick and viscous that some feel imbibing it is more like eating an oyster — the stuff must be swallowed whole. The renowned goblin alchemist Marin Noggenfogger was the first to create this bizarre concoction. The elixir requires a variety of strange ingredients, including the moisture found within the exceptionally rare thistleshrub dew collectors found only in the Tanaris Desert. The means to create Noggenfogger elixir is a secret known only to a few goblin alchemists, who guard the secret jealously. Noggenfogger elixir is typically sold in bottles of 5 doses, although this varies depending on the vendor.