One element could be the fear of failure. In the highly competitive world of drag, Trixie Mattel might constantly worry about not living up to the expectations. If she has a bad show or a negative review, it could feel like a horror for her.
It could be that Lucifer has some valuable lessons or wisdom to pass on to Trixie, and a story is a great way to do that. Stories can often make complex ideas easier to understand. For instance, if he wants to teach Trixie about the consequences of lying, he can tell a story about a character who lies and then gets into a lot of trouble as a result.
It could be a story about some heroic deeds in a fantastical world. Lucifer might be sharing an adventure story where the characters face great challenges and overcome them. For example, a group of brave warriors fighting against an evil dragon to save their kingdom. And Trixie is listening intently, imagining herself as one of those brave characters in the story.
Well, one aspect of a Trixie Mattel horror story could be the idea of her facing a really tough and cut - throat competition in the drag world. There might be backstage dramas where she has to deal with jealous rivals who try to sabotage her performances. It's like a horror in the sense that it threatens her success and reputation.
Well, it's not mandatory. But watching Toy Story 3 first might give you some background and enhance your understanding of the characters and their development. However, you'll still be able to follow and enjoy Toy Story 4 on its own.