Short version: Fanpop launched its alpha release in April 2006 (except back then it was called fanspots). Then the site was launched its beta release with the fanpop name in August 2006. Fanpop's official launch (out of beta, as a "finished" product) was on 1 January 2009.
If you hunt through the image gallery in this club, you'll find screen captures of both the fanspots and fanpop beta logos. If you are interested in reading my perspective on the site's history and development (well, the first two years, anyway), you can read
link.