15 Biggest Plot Holes And Inconsistencies Where ‘Supernatural’ Ignored Its Own Logic

The Season 1 episode "Phantom Traveler" introduces the word "Christo" as a way to expose demons, as hearing the name causes them to show their black eyes. This sounds like a very convenient way to find demons, especially considering how frequently the Winchesters come across them in the future. However, the word is never used again, with the only other reference appearing in the Season 14 episode "Optimism," where Jack uses it on someone who isn't a demon.

It wasn't explained why "Christo" was phased out, although it's clear it was ignored by the show because it would've made fighting demons too easy.

The purpose of averting the apocalypse in Season 5 is to avoid a world-ending scenario. It's mentioned by several characters that Michael and Lucifer's battle would destroy half the planet, which motivates Dean not to give Michael consent to possess him.

However, this battle is actually seen twice, with the first instance being the Season 12 finale, where Alternate Michael empowers Dean and fights Lucifer, who is even more powerful than normal due to stealing Jack's powers. It takes place again in Season 15's "Inherit the Earth," where the main-universe Michael fights Lucifer. There is no collateral destruction on either occasion, despite Lucifer meeting his end both times.

The Levitathans use a domesticating substance to mind-dull humans so that they are easier to finish. By Season 7, Episode 22, "There Will Be Blood," this substance has been added to corn syrup, meaning it's all over the country, forcing Sam and Dean to eat fruits and vegetables to avoid being mind-warped.

Although ganking Dick Roman means the Leviathans have lost control, the characters go back to eating anything they want even though production had been on a national level. Logically, the food should still be contaminated around the country, but this is altogether ignored.

When Dean is sent to 1973 in Season 4, episode 3, "In the Beginning," he meets a young John Winchester. Here, John's acquaintance specifically asks him to say hello to his father, to which John agrees.

And yet, the Season 8 episode "As Time Goes By" shows John's father Henry time traveling from 1958 to 2013, where he meets his grandsons and perishes in the future. It's also stated that John thought his father abandoned him his whole life, but that shouldn't be possible if he was supposed to have a father in 1973. 

The original Death claimed he was strong enough to destroy God, and Lucifer was shown to fear him, as archangels aren't as powerful. In Season 15, episode 19, "Inherit the Earth," Lucifer is resurrected by God in order to snag his death book from the Winchesters. Lucifer takes the life of a Reaper named Betty to turn her into the next Death, as this is the only way for a new Death to be made.

While Betty is confirmed to have Death's powers, she is somehow slain by a simple snap from Lucifer after she reads the death book. Betty should have been more powerful by that point as the new Death, meaning this should have been impossible since Lucifer is an archangel.

The Season 13 episode "Funeralia" reveals that so many angels have perished that Heaven is crumbling. Naomi claims that only nine angels remain in Heaven, and losing anymore would lead to Heaven's destruction.

This point is never touched upon again, seeing as a bunch of angels are slain later on with nothing happening to Heaven. There isn't any ruler left by Season 15, before Jack takes over, but even that doesn't make any difference.