you ask about demonic apparations. yes there are many.
Indeed, after Lourdes occurred, there were over 100 "copycat" visions. Most were merely vivid imagination, but probably a few were demonic. That is why the church is so slow at approving of a vision. Even in today in the USA I know of at least 10 people who were seriously investigated for having visions. Most have been "shut down" by the local bishops, and at least one (bayside) is powerful but so anti church/hateful that some suspect it is demonic...
If you want to read about it is detail, check out the book " A Still Small Voice" by father Groeschel.
http://www.amazon.com/exec/obidos/tg/detail/-/0898704367/qid=1063020125/sr=1-26/ref=sr_1_26/002-9773405-1067262?v=glance&s=books He is a psychologist, and explains how supernatural phenomenum can be anything from fraud to mental illness, to overactive imagination, to spiritual inspiration where a person adds his imagination to pure miracle.
Many churches had "words of knowledge". Now, most Christians who read the bible have inspirations from God, but often these inspirations are contaminated by our selves. So these churches require and interpretation by another, and a Biblical confirmation.
Catholics do the same. ALL confirmed visions essentially say the same thing: Repent and pray. Some have warnings, but others do not. Alas, the warnings are often made more important by people than the message of repentence...
What I'm wondering about, though, is not the deceptive apparitions where a malign spirit appears as a "bright angel," but how the "aliosque spiritus malignos" might appear if they weren't trying to fool anybody.