When I was watching the remake of A Nightmare on Elm Street (2010), my panicky friend told me to tell her when the dream sequences started. How was I supposed to know? No one was wearing the trademark Christmas Sweater except for Fred, so there was no way for me to tell. Except for, I realized, the fact that whenever a dream sequence started, everyone's clothing would have a small portion of red and green on it, and the background would have some noticeable thing be red and green, e.g. the swimming lane markers during the pool dream.— chloeravenblood
The moment I got done watching Wes Craven's New Nightmare, I realized that the plot sort of justifies the In Case You Forgot Who Wrote It title in a strange way, whether on purpose or otherwise: Wes Craven plays himself in the movie, and the whole plot is sort of kicked off by him trying to write another Nightmare On Elm Street film. And to top it off, the script he's writing is based on nightmares he's been having in-story. Thus the film actually is about Wes Craven making (as well as having) a "new nightmare". -Mike K
In the fourth film, Freddy killed Joey by drowning him. This was actually a legitimate tactical method, considering he knew from the previous film that Joey had a powerful sonic scream ability which would be useless without the oppertunity to breathe.
That may also account for the window-shattering effect of Alice's scream when Rick is killed. It's conceivable that Kristen didn't just pass on her own powers to Alice, but - thanks to her becoming connected to the boys as Freddy absorbed her soul into the gestalt - Joey's and Kincaid's as well. Alice didn't really know Joey or Kincaid very well, so didn't know enough about them to recognize this or make conscious use of their abilities, but Joey's sonic scream still manifested when Alice was under extreme stress, the same way Joey himself shattered those mirrors in Dream Warriors.
Alice's victory in The Dream Master seems like New Powers as the Plot Demands, especially considering that Freddy's had no trouble with mirrors before. But in a sense, it's just a different application of a power which was already established in Dream Warriors: the ability to draw people into dreams, either one's own or (as implied by Nancy's death) a "beautiful dream" paradise. The only novel twist is that, rather than drawing people from the waking world to a dream, Alice was drawing them out of whatever gestalt captivity-dreamscape Freddy keeps his victims' souls bound within, and into the dreamscape where she was confronting him. Kristen might've been able to do the same, had she only possessed the necessary imagination or insight into how to stretch her abilities.
In the remake, Freddy molested Nancy and her classmates. There were probably other classes before them.
In Dream Warriors, there's a mention of a Westin Hills patient who cut off his own eyelids to stay awake. No one ever figured out how the patient managed to get his hands on a blade, to do such a thing. Given how Kristen got committed when she awoke from a Freddy-induced dream to find herself holding a razor blade, bleeding, it's possible that this unlucky boy was also mutilated by Freddy for sport, then woke up before the killer could finish him off and was wrongly blamed for inflicting his injuries on himself.
Hypnocil seems like an effective defense against Freddy, but Freddy Vs. Jason reveals that it can potentially render long-term users comatose. There are two possible explanations for this. One is that the drug actually does put people into a coma, which means Nancy was extremely lucky to make it through the years between the first and third films without winding up comatose. The other is that Hypnocil actually has no such side effect, but Freddy - not wanting to let some mere medication spoil his fun - has been capturing victims alive, Joey-style, the instant the medicine wore off, in a calculated attempt to discredit the drug. Either option is pretty horrible.
Hypnocil was stated as "experimental" in Dream Warriors, and noted as still being "experimental" in Freddy vs. Jason. Some twenty years have gone by and this drug still hasn't made it through the FDA approvals process? This indicates that there is, indeed, something very wrong with it, and its use at Westin Hills is pretty much intended to be the best of bad options. The comatose patients who "were given too much Hypnocil" may be from long-term use, or may be because it's a very finicky drug to dose correctly, and overdoses send people into comas. Which means that Nancy was, indeed, very lucky that she didn't accidentally overdose herself.
And depending on if you go along with the idea that the 2010 remake offered, where people (in the remake, Nancy) can still dream even in a coma state, Freddy has access to all those people in the unending comas that they got as a result of the hypnocil that was supposed to keep them from Freddy in the first place. Forever.