The UPA production of Edgar Allan Poe’s “The Tell Tale Heart” is the first cartoon to be certified as unsuitable for adult audiences.
According to America’s Film Legacy: The Authoritative Guide to the Landmark Movies in the National Film Registry, “The Tale Tell Heart” was distinct from mainstream animation because it attempted to tell a serious story in serious manner, without jokes or humor (p. 480).
Here is an excerpt from Poe’s short story:
It is impossible to say how first the idea entered my brain; but once conceived, it haunted me day and night. Object there was none. Passion there was none. I loved the old man. He had never wronged me. He had never given me insult. For his gold I had no desire. I think it was his eye! yes, it was this! He had the eye of a vulture—a pale blue eye, with a film over it. Whenever it fell upon me, my blood ran cold; and so by degrees—very gradually—I made up my mind to take the life of the old man, and thus rid myself of the eye forever.
Now this is the point. You fancy me mad. Madmen know nothing. But you should have seen me. You should have seen how wisely I proceeded—with what caution—with what foresight—with what dissimulation I went to work!