Goofs

When the peach goes rolling down the hill, it rolls along the top of a fence, getting the fence stuck in its sides in a counter-clockwise descending spiral. Once the peach hits the water, though, every scene after shows the fence in a clockwise descending spiral, when viewed from above.

James draws a picture with his crayons, starting with a boy with wings. In the second shot of the picture, the boy with wings is different i.e. it's a completely different drawing.

When James is going to release the candle balloon, the candle is lying inside the balloon. In the next shot, the candle is standing upright on the chair next to the balloon.

There is no way James's aunts could have driven across the ocean from England to New York. Cars can't float on water and one would not survive in a submerged car. Even so, it's impossible to drive at a comparable distance in the time it took for James and his insect friends to travel to New York.

Correction: This is not in any way a movie mistake. It's literally a fictional fantasy movie. By your logic, the whole movie should not even exist as peaches can't grow to that size, float across the Atlantic and land on the Empire Building; little boys can't turn into animations; and insects can't talk etc.

Miss Spiders silk comes from a spool contraption hidden in a compartment on her back, instead of having biological spinnerets on her rear abdomen.

James gets out of bed in his nightshirt, fights his aunt and falls down the stairs head first. His night shirt slips up and reveals that his stunt double is wearing white pants down to his knees. The next shot of James at the foot of the stairs shows that he's not wearing pants.

When they finally realize they can eat the peach, when Spider tosses her peach juice up and backward at Centipede, you can briefly see the wire the animators used to guide the splash.

After James looks at the map and figures out that they are going to New York City, the Centipede spins his Cigar in reaction. Two filament lines attached to the Cigar that were used to suspend it are clearly visible.

The newspaper at the end sets the films date as taking place in 1949; however, the packet of crisps that James takes out of the bin to eat/draw on are Tayto Crisps which weren't founded as a company until 1954.

The start of the film is meant to be set in England; however, the paper bag that James steals from the rubbish bin is a packet of TAYTO Crisps, which are exclusively sold in The Republic of Ireland.

When Spiker and Sponge are in the car attempting to drive away from the peach Spiker is the driver on the left side. She should be driving on the right side of the vehicle as they live in the English countryside.

James addresses Jane Leeves's character as 'Miss Ladybug'. Being British he ought to have said 'Ladybird'.

When the Centipede, the Spider and James are trying to get the compass from the pirate ship, the Centipede pulls the string twice to signal to the other bugs to pull them up. But the Centipede was not there when James told the other bugs to pull them up when he yanked on the sting twice.

At the start of the movie, the narrator states that a rhino appears out of nowhere and eats James' parents. The aunts bring up the rhino several times during the movie. It's later revealed that the rhino is just a bunch of smoke and noise, which makes no sense because that same rhino ate James' parents. Perhaps the biggest error of all is the fact the whole thing with the rhino "appearing out of nowhere" is never explained. In the book, James' parents are eaten by a rhino that escaped from the London Zoo while they were shopping at the market. The book explains it, whilst the movie does not.

When the grasshopper is yelling at the centipede and calling him a disgrace, he misses out 'family' between 'order' and 'genus' when listing the taxons of classification. Someone as intellectual as he is wouldn't make that mistake.

The Grasshopper addresses James at one point as "Sir James". This is an incorrect term of address for him. The polite way to address him in the time this film is set would have been "Master James".

When Spiker swats the moth, her flyswatter clearly hits Sponge's thumb, yet neither reacts to it.