I'm sure he's talking about a scene in a cartoon that's not all that scary but the person posting about it makes a big deal out of out.
Though if we're gonna talk about nightmares, I remember a feeling I had when dreaming about the concept of infinity. I've had this dream since I was young and I can remember it perfectly. I get this feeling like I'm on a rollercoaster, where my insides are pulled this way and that, as I attempt to pick exactly one number out of an infinite amount of numbers.
It's visualized as an impossible amount of orbs stacked on top of each other. I can't escape until I pick the right number. These stacks go further and higher than the eye can see. It would be like multiplying a billion by a billion for every second that you can stay awake and then trying to remember the exact time of day you started so you can keep count. It always gave me a sick feeling in my stomach and that wasn't even the most interesting dream I've had.