The CARET drones, or the Isaac drones, are hands down the best, most interesting UFO hoax ever created (in my opinion at least)

It involved pretty decent photoshops or CGI; placing evidence in private discussion groups totally unrelated to UFOs; detailed fake documents; possibly an entire constructed language and script; and roped in a fairly (in the field) well-known UFOlogist in the form of Linda Moulton-Howe.

And nothing ever came of it. No books or reveal it was viral marketing or anything