Speaking of Life on Mars....

In order to close the city mouse/country mouse, modern cop/retro cop circle, the followup to the original series should have put Gene and Sam into Sam's world (Gene going straight there, bypassing the quattro phase and all steps in between). A complete cycle would then require both of them to inexplicably jump 30+ years into the future, a scenario which would likely be executed in appalling fashion but could be fascinating if done with a bit of panache and speculative brilliance.