Battlestar Galactica The Resistance

None of the cast and crew involved with the webisodes actually got official credit for it, and this led to a legal battle between the Writers' Guild of America and NBC/Universal about how to handle internet-based content. Previously the internet-only content that TV series produced tended to be little more than extended trailers for the series, but Battlestar Galactica made an actual "bonus episode" which was a serious attempt to make an extra episode and actually advance the plot, which led to serious concerns about payment for them.