Just one thing to add...
I see a few people brought up the flicker rate, and yes, 29.97 FPS does indeed hypnotize the viewer. But as for putting in subliminal images of murder
in a children's show, I can say that that's impossible.
I have some experience in making subliminal videos, and I know that if you replace 1 frame in a video with a specific images, the eye DOES pick up on
that.
The only way to insert subliminals is through not-very-large text that appears on the top of the screen for 1 frame.
Another way is to flash a picture for NO LONGER THAN 10ms, and televisions do NOT have that capacity.
So, there are a few issues with subliminals.
1. They are not too hard to pick up on
2. With TiVo, you can go frame-by-frame through a suspicious scene.
P.S. I made a subliminal video with the theme: "drink vodka, vodka is cool"
Tried it out, and it ACTUALLY WORKS!
Only...
Airing something like that on TV will PROBABLY not work.


But a blended image in a single frame is seriously all it would
take to subtly warp a childs mind.