The Anime Movie was Created In-universe after the Events of the First (or Second) Book. And Howell was the director.
Lettie moved to Louisiana after the war.She married a nice, rich man but after giving birth to their daughter she either died or divorced her husband, never to appear again. Anyway, three guesses to what her daughter's name is.. Charlotte LaBoeuff!
Movie Suliman taught Howl before he moved to Ingary.She describes Howl as "her best student", but in the books Penstemmon tutored Howl in magic. Perhaps she taught Howl before he came to Ingary, and he learned how to travel between worlds from her, then studied Ingary's magic with Penstemmon.
One or more of the characters is a Time Lord
Film!Sophie only suppresses her curse, she did not break it and never will, because there is no curse.The witch says nothing about the conditions to break her curse, only Turniphead's. Sophie is shown throughout the film as appearing as old as she feels but with grey hair, and her new significant other Howl can likely see a person's true form as easily as looking through the reflections on the surface of water. The Witch stole Sophie's age age while flying through her in order to fuel her own magic and "beauty", and Sophie is only young as long as her willpower and emotional state allow her to get over the mere fact that she's not whateverteen any more (except in the chronological sense).
The entire movie continuity happens in the same continuity as the book, to the descendants...of the main characters of Castle In The Air.Well, it made sense when I thought of it. Those characters were much more standard and chivalrous, unlike the Belligerent Sexual Tension and lovely snark-war that the original Howl and Sophie had.
Film!Howl is really a Tengu.
Film!Howl is somehow related to Haku.They have a very similar appearance. The Borrower Arrietty, with facts from both the book and the movie versions of Howl's Moving Castle. At the end of the The Borrower Arrietty, the ending is ambiguous (Japanese) or he lives, (American). I posit that the answer is both, that is, he died in Japan, but he lived on in another dimension, the dimension from HMC. Sho's surgery didn't work, and his heart was going to fail early, and he was going to die young. Hearing of this, his estranged uncle (maybe "Jessica"'s estranged husband?) from a different dimension heard about it, and decided to bring his dying nephew to his dimension, and the house and the flowers, so he'd have a chance to see it before he died. While there, though, Sho found about the falling stars, and made a deal with Calcifer when he fell. Calcifer kept his heart (and him) alive, but Sho's personality changed due to a mix of his heart being gone, and actually having a chance to live. However, because he didn't know if actual magic existed in his world (oh, yes, there were the Borrowers, but did that mean magic?), so he "died" in Japan, and decided to live the rest of his life in the dimension where he could learn magic, and where his heart was "safe". Years later, "Howl" makes a name for himself, and meets Sophie, and the events of the movie happen. Now, in the book, Sophie was able to speak life into things, and will things to happen because of magic. In the movie, Sophie does the same thing, unconsciously, and that along with years of being magically healed by Calcifer, his heart was fine, and he lives the rest of his life with Sophie.
Sophie never wanted to have children. She is quite protective of Morgan in cat form during Castle in the Air, true, and in House of Many Ways also seems to look out for him a great deal. But there was some awkwardness there, right around the time they both were transformed back into humans. She was quite wary of holding him, for instance, and even Howl was better at taking care of the baby. She seemed too uncomfortable with the whole thing of being a mother. When Lettie had her daughter at the end of the book, though, she was just thrilled to be an aunt. So it's not something like not being particularly fond of children. I think that she does love her son but would have preferred not to have any children and just be with Howl. Most likely, the pregnancy wasn't planned, and having a child took her by surprise.
Howl and Sophie will have a son.