James and the Giant Peach/WMG

The old man was a young Time Lord.
The Doctor had stated that he was trying to be old and mature when he was young to seem important and grand, and as he aged, learned to lighten up and cut loose a bit. So, another renegade Time Lord (there was like an entire generation, after all) with the same mindset is born, steals a TARDIS as well and goes off. He comes across James, and much like the Doctor, is compelled to help. The weird mix? It's either just a joke, or it really is made from that stuff, with some alien tech thrown in. The rhino? Somewhat blotted out memories of a Judoon attack.

The Rhinoceros is a Heartless.
It's black and shadowy with glowing yellow eyes and is apparently being controlled by two very nasty people. Also, it eats people despite rhinoceroses being herbivores usually.

The peach-travel part of the movie is an acid-inspired dream.
The "crocodile tongues" are a potent mix of just about every hallucinogenic substance known to man and James, so miserable that he'd take anything offered by the first person who'd shown him even the smallest bit of kindness since he came to live with his aunts, was willing to accept the "witch's brew" answer at face-value. What really happened is the priest Spiker charged double called Child Services, who discovered that relatives of James's were living in New York City and took him there while he was asleep and tripping balls. (Still a happy ending, but seriously, that shark could only have been seen with, erm, outside assistance.)

Going with the above, Spiker and Sponge are the witches Mingella and Blobbelda from Banjo Tooie
... prior to going on a cracking crocodile tongue trip!

The film's robot shark was a Deceptacon.
It had red eyes and shot at anything that moved. It might have also been used for more unsavory purposes, as the begining showed.

The man who gave James the crocodile tongues was his dad.
Well, we don't know about his mom still, but think about it. He knows what James has been through as though he's secretly been keeping an eye on him throughout his whole life... and with some rough years gone by, it looks like he really could be his dad.

Spiker and Sponge made up the rhino in means of explanation. They killed James' parents.
The rhino James encounters later is simply a thunderstorm, and due to his fear of rhinos (due to the aunts' fabrication), he sees it as one.

When the man who gave James the crocodile tongues said that all of his wildest dreams would come true, he meant the good as well as the bad.
Yes, the tongues gave him friends and an escape from his horrible life with his aunts, which is all that James ever wanted. Just like that island in Voyage of the Dawn Treader, however, the thing that brings people's greatest daydreams to life also brings to life their greatest nightmares. The mechanical shark? As stated on the main page, it spits out the same fish heads that James's aunts fed to him at the beginning of the film that he was so disgusted with. Likewise, the cloud rhino was a product of James's fear of the rhino that killed his parents. This even extends beyond merely creating physical beings. One of James's worst nightmares is that his aunts will somehow find him and make him return to his old life. This would definitely explain how Aunt Spiker and Aunt Sponge were somehow able to drive across the ocean, judging by the state of their car: James's fear was brought to life by the tongues and gave them the ability to do so.

The man with the crocodile tongues was a magical supervillain who intended for James to obliterate reality as we know it.
He gave the kid a whole jar of these things, just one of which can mutate a peach and several bugs inside it. And he didn't intend for James to drop them all on a barren rock. He encouraged James's dream to travel to one of the most populated areas in the world and to take the tongues there with him.

The Rhino from the film was a thunderstorm.
Don't know how obvious this is, but I'm throwing it out there. James and his parents were watching clouds and picking out shapes. A thunderhead rolls up on them. James thinks it looks like a charging Rhino. Pa and Ma James get struck by lightning. James thinks the Rhino killed them. James' aunts are asshole enough to make fun of him for it. James sees every thundercloud as a rhino from that point forward.

The Rhino at the end was Gozer
It came across the peach at just the right time for poor James to unintentionally choose the new Destructor Form.

Jack really was the pirate captain
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Most of the film version took place in James' head.
I know that's cliched- every WMG has that- but hear me out.

- In the opening song James talks about retreating into his mind when he's scared.

- The surreal tone- the mecha-shark, the bizarre cloud rhinoceros... James invented them.

I always took the "rhino" that the aunts claim killed James' parents to be a lie. Something far worse killed them and the aunts tell James it was a rhino. Anyway, just a thought.

The bugs were never bugs
They were really humans, James just saw them as bugs.

Let's just say that the Crocodile Tongues were hardcore drugs. They made James go completely nuts. So, the Peach wasn't a peach (maybe it was a boat?). But nonetheless, he escaped his aunts and went to the "peach". On the inside, he met men and women with names that were of insects (and arachnids), and that only supported his drug-crazed theory that they weren't human. Miss Spider was French, Mr Centipede was from Brooklyn, and so on, with the Glow-worm being an elderly woman and the Earthworm being a blind, paranoid man. They all took off in the peach-boat and went through their adventures.

Halfway through, maybe the boat crashed and they had to replace it with a fallen airplane they came across (maybe it was called the "seagull").

James' hallucination never wore off, causing a few people to believe him crazy, but it made a good enough story for his new friends anyway.