10 Craziest Doctor Who Time Loops

Heaven Sent might be the best story on this list, but in terms of the scale and power of a singular loop, The Armageddon Factor's universe-spanning loop takes the cake.

The Key To Time is responsible for this one. It's one of the most powerful items in Doctor Who lore, used by the Guardians to maintain the very fabric of time itself. So, given its timey-wimey properties, it's no surprise that the Key is capable of whipping up a cheeky time loop, which is exactly what the Fourth Doctor uses it for in this 1979 serial.

Here, the Doctor and Romana are on a mission to collect the Key's scattered pieces, but along the way, they must stop the war-mongering Marshal Of Atrios as he tries to attack his neighbouring planet of Zeos. Solution? Trap him in a time loop!

The Doctor uses the Key To Time to generate this loop, but because the device is incomplete at this point, the effects of the loop inadvertently reach across the entire universe, prompting the Doctor to utter a rather fabulous quip:

"Just imagine... somewhere, someone's just slipped on a banana skin, and he'll be wondering forever when he's going to hit the ground."

Fortunately, everything soon reverts to normal, allowing banana-man to hit the ground with a ruddy great wallop. Nice one, Doctor.