Memory Alpha wrote:
During the fourth season , there were efforts to write an episode that included a role for William Shatner. (Inside the Mirror Episodes, ENT Season 4 DVD special features)
One of these early concepts involved the mirror universe . At the Grand Slam XIII Star Trek convention in March 2005, executive producer Manny Coto recalled, "We had talked about doing a mirror universe episode ever since we got into Season 4. But then we had the possibility of getting William Shatner. Coincidentally, the Reeves-Stevens [Judith and Garfield Reeves-Stevens , who had worked with Shatner on several Star Trek novels] were a pair of writers whom I desperately wanted to bring on the show. And they, it turned out, had an idea for a mirror universe two-parter which would feature the return of William Shatner." [X] wbm
At the same convention, Garfield Reeves-Stevens explained, "The idea was that the Tantalus field was not a disintegrator, it was a humane way of dealing with prisoners, by sending them back in time to a sealed penal colony . Enterprise (NX-01) comes upon the colony – and Tiberius [ mirror-Kirk ] is there. Tiberius thinks, 'Finally, a ship with a transporter – I can get back to my own universe, my own time.' He basically goes on the NX-01, gets to the transporter, sets it to go back to the mirror universe – the mirror universe doesn't exist." "It hasn't been created yet," Judith Reeves-Stevens added. Garfield continued, "So Tiberius and Archer work together to figure out where the division point is between the universes, what point that one split off into the other. And as it turns out, Tiberius and Archer together are responsible for the creation of the mirror universe." [X] wbm William Shatner himself pitched this story concept to executive producers Manny Coto, Brannon Braga and Rick Berman, over lunch. The idea was well received by Coto, Berman and Braga. However, Berman then pitched an alternative concept, this one having been devised by Mike Sussman . The idea was totally unrelated to the mirror universe and involved Shatner playing Enterprise's Chef , who Daniels would bring into the future to preserve the timeline by successfully posing as James T. Kirk during an important event in history. As Shatner and Paramount were unable to reach an agreement, the plans to have him included in the series were discarded. [X] wbm However, the desire to visit the mirror universe remained, and resulted in the production of " In a Mirror, Darkly " and " In a Mirror, Darkly, Part II ".