Right before Asterix and Obelix start the Pleasure Island task, Caesar pulls a genuinely creepy Slasher Smile followed by an Evil Laugh, after pondering whether Asterix and Obelix will survive the next task (the Pleasure Island). This is immediately followed by a shot of the Roman senators trying to hide under the table, being just as creeped out as the viewers, brilliantly lampshading this, but not quite managing to serve as Nightmare Retardant.
Iris, the Egyptian hypnotist, is pretty spooky, with his glowing eyes, not to mention making people think they are animals. And his deep bass voice in French.
The Cave of the Beast. The place is full of Surreal Horror. The monster head-shaped entrance and sound of the wind storm itself before Asterix and Obelix enter the cave are already bone-chilling, and that's just the beginning.
Surreal Horror in comparison to the rest of the Cave, but it's apparently an Eldritch Location capable of warping time and space, as Asterix and Obelix briefly find themselves in a modern subway station (the Alesia Station in Paris, to be exact). The two can't make heads or tails of where they are, and when the lights cut out again, they're back in their own time.
The Place That Sends You Mad. The House itself isn't that terrifying, but seeing the effects is, especially when there are some genuinely terrifying things among all of the kid-friendly crazies. While a woman running down the street acting like a chicken is funny, the man with a Slasher Smile, following her with an axe and chopping wildly... is unsettling.
As amusing as the crazy antics are, it is very unsettling to see a bunch of annoying yet normal Obstructive Bureaucrats driven stark ravingly spare in mere minutes. The worst being the beloved hero Obelix nearly losing his marbles and going on a demented spree, cackling and spluttering madly all the while. Thanks Toutatis Asterix is able to calm him down but still... As a nerve-wracked Obelix Lampshades, this is the first time our Showy Invincible Heroes face something they cannot defeat with punches.
When the Prefect realizes that he has just given the elusive permit away, he joins the madhouse by blowing on a horn and giving off a really disturbing insane cackle. The camera slowly fades away with the mad look in his eyes being the last to go (including a red glow flickering all the while) and finally the demented sound of a completely broken mind keeps echoing through the darkness.
For the eleventh task, Asterix and Obelix have to spend the night on a haunted former battlefield, where a whole legion of ghosts of Roman legionaries awakens. Like the Cave of the Beast, it's really spooky (especially with the spine-chilling music)... until the moment Asterix starts to argue with the centurion ghost. At this point, Hilarity Ensues.
in Paris, to be exact). The two can't make heads or tails of where they are, and when the lights cut out again, they're back in their own time.