No, the melange of stuff approach is not an approach I've seen outside the CC/Heidi/Ebony crowd in HP fandom or in any other fandom.

What is not uncommon is to have a half-dozen TV quotes or so in your story, or to use some of the HP canon scenes or lines to rewrite something from another character's POV.

My understanding of this argument in years past was, "If it's okay to use one line, it's okay to use a bunch." I disagree with that. However, the fact that I've seen the argument so many times has made me very uncomfortable with using any quotes or references at all. The argument also extends from, "Well, we're infringing on copyright anyway-- what's a little more infringement here and there?"

But, basically, either you're writing under your own steam or you're not.