Television is and always has been about rules.
There are certain words you can't say, things you can't show, people you can't talk about, places you can't go, music you can't use. It's a real pain when you think about it.
But what's that old expression? Rules are made to be broken.
Nothing can grow and evolve if it sticks to what came before it and TV is no exception. Without writers and producers taking risks, we'd all still be watching boring adaptations of Shakespeare in black and white. And nobody wants that.
The following ten TV shows all changed up the formula and, for the most part, that was a good thing. In some cases, the innovations that these episodes started have now themselves become rules and conventions! Funny how it goes like that sometimes.
Whether it was depicting things that had previously been unseen, messing around with establishes formats, or just throwing a whole heap of stuff at the wall and seeing what stuck, these ten episodes are all ground-breaking in their own way and are still as exciting and memorable now as when they first aired.
10. The Tenth Planet: Episode 4 - Doctor Who
Regeneration is one of the defining traits of British sci-fi classic Doctor Who..
The ingenious idea to give Time Lords the ability to change their faces and bodies when they are sick or wounded was first invented to get around the failing health of William Hartnell, the first actor to play the Doctor.
Hartnell's final bow came in the finale of the four-part serial, The Tenth Planet, in 1966. Throughout his battles with the Cybermen, the Doctor grows weaker and weaker, eventually succumbing to old age at the end of the episode. His first body dies and he is reborn with a new face and a new actor, Patrick Troughton.
This episode completely changed the game when it came to the format of Doctor Who. The show had given itself the ultimate get out of jail free card - if an actor playing the Doctor gets sick or wants to quit, then the showrunners can just hire a new one without disrupting the continuity of the show.
It's a brilliant idea that has kept Doctor Who on TV for decades and will keep it going for decades more to come.