"Charmed and Dangerous" was originally meant to be the fourth season finale, with the following story lines used for the fifth season and "Charmed" (2002) {Long Live the Queen (#4.20)}_ was to be the 100th episode.
The Angel which guarded the Hollow, is the only Whitelighter throughout the series to be seen with a Halo.
Title was based upon the expression "armed and dangerous" that has been used as a title in various medias.
In the seer's vision, we can see that the sources hands are grey in color. When we see the source just before opening credits, his hands are not covered in grey make up.