1. The Land Of Wooden Doors
It has been a long-running gag for writers - of the new Doctor Who series in particular - that despite all his boastful references to its flashy settings, the Doctor's sonic screwdriver can be kind of inept at times. In series one, Captain Jack Harkness made fun of the screwdriver because it wasn't a sonic blaster, and throughout Tennant and Smith's series, it's been noted that the screwdriver just "doesn't do wood". Imagine the Doctor's surprise if he landed in a world riddled with locked wooden doors! Watching him squirm in frustration would not only be hilarious, but would also give rise to the potential for many different scenarios - whereby the Doctor might become trapped by an enemy and would have to invent some other clever way to escape his doom. He's going to have to invent a setting for wood. It's embarrassing.