The Gnoolies: As mentioned on other pages, their bite causes one to be continuously divided by random numbers until you become one of them. What happens when you constantly divide? You get closer and closer to zero - nul. You could also think of the name being a contraction of "nearly nul", since you can't ever reach zero by division.
Just how would Wonka know what it means when you're bitten by the creatures in Minusland, and how you don't know you're bitten until you are?
He could've witnessed someone else get bitten and transform, or he could've encountered a description of the effects at some point in his journeys (perhaps he stumbled upon an Apocalyptic Log by one of the Gnoolies' victims?).
If he did know firsthand, though, maybe that was why he needs a successor so badly, why he looks so much younger than his chronological age, and why he doesn't want to waste Wonka-Vite on himself?
If a person who takes the aging medicine gains new memories, does a person who takes the youthening medicine lose memories of the last 20/40/whatever years? If Charlie's grandparents or parents had taken a sensible dose, would they no longer recognize Charlie?
Maybe this is the reason Wonka was willing to retire, rather than taking the medicine - he didn't want to forget his brilliant inventions of the past 20 years.
Based on the demonstration case, it doesn't seem likely that Wonka-Vite makes people lose memories; the Oompa-Loompa Wonka tested it on was able to remember being seventy before he took the pill, and then work out that he had become fifty once again based on how he remembered feeling at that age.
If the Space Hotel had "newspapers and television shouting about almost nothing else for the past six months," how come we never heard a word about it in Charlie and the Chocolate Factory? Not to mention that the furore over the Golden Tickets is now a part of the "almost nothing else".
Considering that Charlie and his family live so close to the factory, the news may have focused on the search for the tickets as that was more relevant to the locals.
