"Rabbid Dreams", especially the climax where a Rabbid is dreaming that it speaks perfect english and reveals that all this time the Rabbids' plan is to conduct experiments on humans.
The Rabbids themselves aren't so easy on the eyes considering their eyes are bulging out and their mouths open to a disturbingly large proportion. However, they seem less frightening with their mouths closed. Rabbids could be considered Ugly Cute
The confused Rabbid's face in "Rabbid Mozart", although Played for Laughs, is still a bit unsettling.
"Zombie Rabbid": The surprisingly creepy music playing during the entire episode as well as the ending with the horde of zombie Rabbids.
The season 2 premiere, "Being Rabbid" ends with John the Scientist's brain trapped inside the body of a Rabbid, and his boss, refusing to believe him, presses a button that sends John through an underground chute, leaving him trapped him there in a Rabbid body, possibly forever.
"Star Rabbids" has a very creepy shot of four obsessive Rabbids approaching another one they confuse for a television star. Their pupils are huge, their mouths are open wide and there is an eery green light coming from below them. The music playing during this doesn't help.
"Babysitting Rabbid" has two Rabbids confusing a human baby dressed in a bunny pajama for one of their own. What ensues is a series of surprisingly cruel and dark events like having the baby being launched into the air and falling flat on the ground, as well as the Rabbids' "solution" to make the baby happy, which is getting an axe.
In "Mad Rabbid and the Genius Moustache", we learn that the reason Dr. Mad Rabbid became "Mad" in the first place is the result of him frying his own brain by electrocuting himself with a defibrillator machine. For all the times we've seen Rabbids survive hundreds of Amusing Injuries without suffering any real consequences, seeing one of them actually receive permanent damage is extremely terrifying.
Season 3 has a two-part Halloween special called "Freezing Rabbid" in which Were-Rabbid teleports to the scientists' polar base at the Arctic. Both shorts play out like mini horror films with eerie fog, well-orchestrated creepy music and even some slight jump scares. This is easily the most atmospheric episode in the entire series.
The Season 4 Terminator parody, The Rabbid From the Future follows a Cyborg Rabbid sent from a Bad Future to hunt down and destroy a regular Rabbid wearing a blonde wig. The Cyborg Rabbid itself is probably the most terrifying Rabbid character to appear in the show, since it is shown to have no regard for human, Rabbid or any life for that matter, and will destroy anything that stands in its way.
The episode literally opens with the Cyborg Rabbid tipping over and launching a squad car into the air with only one hand.
The scene where the Cyborg Rabbid gets blown up by Torx's Rabbid drone not only comes out of nowhere, but is immediately followed by the Cyborg Rabbid emerging from the flames to reveal part of his robot exoskeleton.
Just the mere possibility that Otto Torx actually succeeded in building an army Rabbid drones that apparently take over the Earth in an alternate future timeline is enough to send chills down your spine.
