10 Terrifying Batman: The Animated Series Episodes That Gave You Nightmares
7. Lock-Up
The premise behind this episode is that there's a new chief of security at Arkham Asylum who is actively torturing and beating the inmates. Eventually he is fired and takes his revenge on everyone involved.
The very start of the episode really dives headfirst into the fear pool with Batman and Robin bringing Scarecrow to Arkham Asylum, but he is petrified, leading to the quote that even made Batman believe something was wrong:
"Don't take me back there, please! Look at me, Batman! I'm shaking. ME! The Scarecrow! I wasn't even going back to crime this time! I just wanted to escape... him!"
SCARECROW - the master of fear himself - said that. But he isn't the only villain to fall victim to Lock-Up - The Ventriloquist and Harley Quinn join him too.
That is where the nightmare sets in. There aren't any monsters to terrorise the viewer this time, but instead an exceptionally cruel individual, charged with a duty of care over the Asylum's inmates.