"Oh The Thinks You Can Think" has the Jibboo, who is depicted as a shadowy, bird-like figure walking toward a small boy in the street in the middle of the night. The caption somehow makes it worse.
What would you do if you met a Jibboo?
In fact the Jibboo makes an appearance in the Paraphernalia Wagon cllip.
Trophy heads of Dr. Seuss creatures.
The 5,000 Fingers of Dr. T, a film written by Dr. Seuss.
The Wickersham Brothers, especially when accompanied by a villain song. It gets worse when their uncles and cousins are introduced.
The "Bitsy Big-Boy Boomeroo" from The Butter Battle Book. The book ends with the fear that one of them will drop it, which is exactly the point.
The entire sequence that we see in the animated adaption has a Mad Scientist feel to it. It starts with red goo that comes to life and moves some controls around, and even features split-second glimpses of ghosts and snakes. The Chief Yookeroo's gravelly voice singing the accompanying song is also unsettling when combined with these eerie visuals.
In One Fish Two Fish, the two children find a large aquatic creature with bright yellow eyes and curved teeth in a big glass jar in the park in the dark. They decide to take him home and name him Clark. Clark will live with them. Clark will grow and grow. Will their mother like this? They don't know.
Technosagery's "Out of the Dark" offers a take on what happened after Clark started growing.
At the end of Thidwick the Big-Hearted Moose, the scene where Thidwick's unwanted guests◊ ended up being stuffed and mounted when Thidwick threw his horns away is a bit disturbing.
In The 500 Hats of Bartholomew Cubbins Bartholomew sentenced to have his head chopped off. He walks down to the dungeon and meets an executioner with an enormous ax. The magicians were pretty spooky too.