Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is a scene from a short animated cartoon by Tex Avery that you can watch here.
We hear an announcer and see a split screen labeled For Grown-ups and For Children: "Ladies and gentlemen, your attention please. The next scene is quite gruesome. So for the benefit of the children in the audience, we will split the screen. The left side for grown-ups, the right for the children. For the grown-ups, a hideous gila monster. For the children, a recitation."
Then we see and hear a little girl reciting Mary Had a Little Lamb on the right, while an animated lizard that's supposed to look like a gila monster (but doesn't) snarls, shows its teeth, and writhes around on the left. The girl finishes her poem and curtsies, then lets out an enormous growl at the gila monster that sends it running away yelping like a scared dog.