Protectors of the Plot Continuum, nearly always referred to simply as the Original Series (TOS) by fans, is the first PPC series, begun by Jay and Acacia. It was started on January 30, 2002, not-so-coincidentally soon after the movie release of The Fellowship of the Ring. The barrage of badfic following that film inspired these two to create the world of the PPC that we all know and love. It has 26 missions in all, and for a long time had the most missions of any agent pair. (Tawaki, Iximaz, and IndeMaat are known to have published more missions than Jay and Acacia, and it is possible others have as well.)
It was originally posted on Fanfiction.net, but was kicked off (quite unfairly, we believe) on May 11, 2002. It found a new home on Philosopher At Large's website, Odd Lots, but that since went down. Fortunately, Miss Cam also archived the series, and almost all of it could be found there until it, too, finally succumbed in 2015. As of 2012, the complete series is archived at PPC: The Lost Tales.
The Original Series ended when Jay and Acacia retired in 2003 and left the PPC to its own devices. Jay has returned to the Board once, but only very briefly.