To be more of a boring killjoy:

You can search on Google and find sites verifying that he made it up himself, but anyone who knows anything about machine learning can tell just by the context of the tweet.

He says he showed a "bot" the movies, and it wrote a script. Only machine learning algorithms would have any chance of doing this (not a "bot"), but they learn from example. If you train a machine learning model on a movie, then it has only ever seen movie frames and heard the audio. Those movies would be the only thing that it knows that exists in the world. It would not know that an alphabet existed that would match the dialog to words. It would not know the typical formatting of a script.

You could try to get it to generate new movie frames and the accompanying audio, but it is very difficult to do this well. Most examples of this can only replicate a few frames of video after being trained on a large diverse set of videos.

To try to do something like this, you would need to show it movie scripts, but only two or three movie scripts would not give it enough knowledge to make things up like shooting horses unless those were in the script. Machine learning algorithms can write silly things, but they are always some sort of reshuffling of things they have seen in the past.