This line from the first chapter of the book: Sophie began to feel that Wizard Howl and the Witch of the Waste should get together. They seemed to be made for one another. Someone ought to arrange a match. This is funny in retrospect, as Howl did court the Witch for a while, and it did not end well at all.
Howl hamming it up and covering the castle in green slime. "Despair! Anguish! Horror!"
Sophie's reaction. "If it wasn't for Calcifer, he could behave like a jellied eel all day for all I care."
All of Howl and Sophie's bickering is funny, but the mental picture this conjures is just hilarious:
Howl: If I were to court a girl who lived on an iceberg in the middle of an ocean, sooner or later — probably sooner — I'd look up to see you swooping overhead on a broomstick.
"I can sense Sophie's hand a mile off. And there are several miles of this suit."
Later in the same scene (all of which is a Crowning Moment of Funny): "I am now," he announced, "going to get ready for the funeral. Please, both of you, refrain from doing anything whatsoever while I do. I can tell Sophie is in top form at the moment, and I want this room the usual size when I come back into it."
Sophie's family trying to clean the castle and complaining about its messiness when they come to visit, in the middle of Howl's battle with the Witch of the Waste.
Howl returning to the castle drunk, singing "Calcifer's saucepan song" (unbeknownst to Sophie, the Welsh folksong "Sosban Fach," which is associated with certain rugby unions). Later, after he's gone upstairs to bed, Sophie hears thumping, and him giggling about how the bed is "dodging" him.
Howl: I assure you my friends, I am cone sold stober!
Sophie's first experience with Seven League Boots, where she marvels at traveling miles in a single step, but then can't stop.
Sophie gets a Captain Obvious moment when she hears that Mrs. Pentstemmon is dead.
"Dead?" said Sophie. She had a silly impulse to add, But she was alive an hour ago! And she stopped herself, because death is like that: people are alive until they die.
After Howl goes out one day, Michael boards up the castle's doors to keep the Witch from getting in. Then someone tries to get in, and they think it's the Witch...
Michael:[to Sophie] Don't be afraid. I'll keep you safe.
Michael grumbling about the trouble Howl falling in love has caused.
Michael: We've had lawsuits, and suitors with swords, and mothers with rolling pins, and fathers and uncles with cudgels. And aunts. Aunts are terrible. They go for you with hat pins. But the worst is when the girl herself finds out where Howl lives and turns up at the door, crying and miserable. Howl goes out through the back door and Calcifer and I have to deal with them all.
When Sophie says a scarecrow tried to get into the castle, Howl, Michael and Calcifer don't believe her. Then, the next day when Howl opens the door, the scarecrow tries to get in.
Calcifer and Michael: There really is a scarecrow!
She seized her parasol and became so very warlike that Sophie had to hold her down. Sophie did not care to think how Howl might react if Fanny woke him by stabbing him with her parasol.
Having obtained something of a reputation as a witch, a young man comes to the castle to purchase a spell from her. He's agreed to a duel, knowing he's hopelessly outclassed, and wants something to give him an edge. Having absolutely no knowledge of how to create a spell, Sophie fakes her way through by sprinkling a healthy dose of cayenne powder into a cloth, grabbing a knife and waving it around over the cloth while muttering to herself to appear suitably witch-like before wrapping it all up. She hands it to him and tells him, "Throw this in the air just as you're about to shoot, and then both of you will stand an equal chance at victory."
Extra hilarious the second time you read because Sophie thinks she's just making up a bunch of nonsense but her latent magical powers mean it will actually work.
Even more hilarious later on when it turns out that it did work! Apparently the man won by attacking while his opponent was trying to dislodge paprika from his eyes.
There's Howl screaming down the stairway, running into everything while pulling at his hair, the green slime itself, and Sophie hauling Howl upstairs while he's covered in green goo... noticing only too late that his towel's slipped off, and he's completely nude.
Markl: He's calling up the spirits of darkness again! ...I saw him do this once before, when a girl dumped him.
Sophie: Well, now I have to mop again.
From the same scene:
Howl: I give up. I see no point in living if I can't be beautiful.
Made even funnier in that it was Christian Bale saying that. Never knew, Bats, never knew...
The mention that Howl once reacted to getting dumped by calling up the spirits of darkness, like a wangsty teenage goth.
If you listen closely, Sophie's tone of voice almost sounds like a Seen It All teacher — kind of fitting given what she's doing.
Sophie is asking Calcifer to let her use him for cooking, and the line that Calcifer says after she forces the pan on him:
Sophie: Let's get cooking.
Calcifer: I don't cook! I'm a scary powerful fire demon! (sticks his tongue out) Leh-leh-leh-leh RAWR!
Sophie: *shoves a frying pan on top of him, smushing him into the bottom of the fireplace*
Howl solemnly reads the spell the Witch of the Waste hid in Sophie's pocket that has left scorch marks, and then moves to erase it while he blithely says, "That can't be good for the table."
Howl telling Sophie why the Witch of the Waste is after him. Sophie just makes a face that says "are you serious?"
In the ending, where Turnip Head's curse is broken. It's the typical true-love's-kiss-breaks-the-spell, but...
Witch of the Waste: Looks like your true love is in love with someone else.
The scene when Sophie goes to see the king, and is trying to figure out what Howl disguised himself as. In the English version:
Sophie: *Sees a flying device with a girl shrieking and giggling with joy above* That could be him.
Just as Sophie and Howl escape Madame Suliman.
Howl: Did you have to bring those two with you? (Sophie glances back and sees old!Witch of the Waste and Heen) Witch of the Waste: Nice doggy. (Heen wheezes) Sophie: I can't believe you work for Suliman. I guess it's too late to toss them.
During the escape, Howl lets Sophie pilot their aircraft for a while, despite the fact that she has zero flying experience.
(Sophie accidentally bumps the aircraft into a tower)
Howl: Wow, you're good!
Sophie: Are you nuts?!
Sophie and the Witch of the Waste trying to climb up the stairs to Madam Suliman's castle. In other words, two elderly women (one a teen trapped in an elderly woman's body, the other, a morbidly obese woman, who, until this point in the film, was the bane of the entire country) trying slowly and desperately to outrace each other to reach Madam Suliman.
"You cold-hearted hag! Next time, I'll turn you senile, too!"
The fact that while Sophie's going up the stairs, she's dragging a ridiculous-looking dog that she thinks is Howl in disguise. She spends most of the scene whispering to the dog, talking to it under the impression it's Howl. Even though it's difficult for her, she carries it up the stairs so she can keep him around, like he promised. Then, she finds out it's a real dog that happens to be Madame Suliman's familiar.
And when Sophie finally DOES make it up the stairs? She then proceeds to act as the witch's own cheer squad. Once the witch reaches the top, she replies, "Oh, just shut up!"
After Sophie confronts Suliman in the palace, the king arrives to tell Sophie that he no longer plans on using magic for the war. Suliman is quick to point out that he's acting surprisingly eloquent... because the real King isn't anything like that. Cue the actual king loudly entering the room, laughing boisterously as he mistakes the disguised Howl for a double conjured up by Suliman.
The way Markl panics when Sophie says she also has to clean upstairs. He dashes upstairs yelling at her to leave his room for last.
"She likes my SPARK!!!"
When Sophie introduces Turnip Head to Markl.
Markl: Are you sure you're not a witch?
Sophie: I'm the worst kind of witch, the kind who CLEANS.
When Suliman's monsters pursue Howl and Sophie at the secret garden, Howl safely drops Sophie off at the portal door. He makes sure that she floats down gently, but she still has to deal with landing on the stone steps, this leads to Markl coming back and finding sprawled and rubbing her bottom:
Sophie: Ohhh, I'm too old to be treated like this!
Howl expands the castle to give it more rooms including a new toilet. When it is formed, the toilet roll jumps out of the toilet onto the holder on the wall.