Star Trek is one of those shows that knows not to mess with a good thing. Usually, quite often the franchise will set up it's premise for a series and adhere to it. The original show had a five-year mission, Deep Space Nine was set on a space station, Voyager was in the Delta Quadrant, and Quark was a mischievous rascal. These were constants that never changed.

Yet, sometimes the formula was put to the test. Star Trek: The Next Generation was set to have Jonathan Frakes and his character Will Riker take over as series lead following the conclusion of season three. With Patrick Stewart waffling about returning, and a perfect exit point featuring The Borg, stars alignd to shift focus.

That was not to be, however, as Stewart and his character Jean-Luc Picard both returned to the fold for season four. Yet, that wasn't the only time a...