The Romans

The first comedy story in Doctor Who's history (and not the last by any means) it mixes pure farce with some darker moments to give the dramatic moments more emphasis and yet it often treats them as dark comedy at the same time. The cast go all out to play the comedy but without taking it too far, they never ruin it by bringing the characters out of the moment, if it wasn't for this story we wouldn't have Zaroff's way OOT celaimations in The Underwater Menace, season 17 or half of the Tenth Doctor's cheeky one liners. The show owes its continued success to this story because it it wasn#t afraid to do something new then later productions probably wouldn't either and the show#s rich diversity would never have happened and the show would probably have been axed when Bill Hartnell decided to leave.