When I started thinking about things I know by heart, the first thing I thought of were song that I like/love. But I realized, to know a song by heart, you'd have to be able to write it down without listening to it and I honestly can't do that with any song and get all the lyrics correct. I can sing along to many songs and get the lyrics right but that's about it.
Then I thought of movies and there is a movie that I definitely know by heart, and that is The Swan Princess. This was the movie that as a kid I would watch, rewind and re-watch all day. I think I burned out the VHS. It's an old Disney style movie, like Cinderella, Beauty & the Beast(both which I kinda know by heart). I know the plot, songs and almost every line of dialog in this movie. How does it affects my storytelling, I'm not entirely sure. The only main thing I can think of is that any story I write has a happy ending and I tend not to dabble in darker, more mysterious stories. Everything for me is pretty "light" and "fluffy" as it were. One quote from the movie that I love and apply to a lot of things is: "Once you steal something, you spend your whole life fighting to keep it." This line wasn't a direct moral of the movie or something that was emphasized, which I believe is why I learned to pay attention to details and like to throw in subtle messages in things I write.
A note on Pluto not being a planet.
I think it's ridiculous that they decided it's not a planet any more. It has been taught as a planet for over 75 years and the only reason scientist decided it's not a planet is because it's made of ice instead of gas. It's now a dwarf planet and to top it off it's not the first dwarf planet, it's the third or something like that. Pretty soon they'll reduce Pluto to a moon since it's so small.