The character of Owen, played by David Mitchell, first appears in Series 1, Episode 4. Owen wasn't intended to be a regular character, but the audience response was so good that it was decided to bring him back permanently for Series 2.

The original pitch of Think the Unthinkable wasn't an audience sitcom. Writer James Cary sent producer Adam Bromley an outline for a non-audience mockumentary, in style of People Like Us. The pilot script had five characters in it, of which only 2 (Ryan and Sophie) made into the resultant series.

Episode 5 of Series 1 is a heavily reworked version of the pilot script. One of the lines that carried over is Ryan saying Could we make London mostly downhill?.