Goofs

Near the end of the movie, a talking screwdriver character comes into the story without any formal introduction, and is apparently a close friend to Pingo, despite it having been previously established that he has a crippling fear of screwdrivers and that they were banned from Atlantis.

Maltravers had gray hair in the previous movie. Yet in this one he has orange hair.

The Cheif Shark's uniform changes from white to blue during the rap scene, but is reverted back to white.

In the first film Maltravers ordered the sinking of the Titanic in order to assassinate the Duke of Camden for his whaling rights, something to which there are several witnesses, including the Prince of Andalucia and the Duke of Camden himself. However, clearly nothing has been done about his crime since he is still a wealthy ship owner in charge of a large naval force in this film.

The two halves of the Titanic were never sealed back together. Neither was the entire ship relocated from the bottom of the Atlantic to the shore of a secret island.

Morse code can't be made with using a set of alphabet letter keys, it can only be accomplished by using a single straight key.

Life vests can't save you from drowning when you are traveling a couple miles down the depths of an ocean.

It's not possible to fire a cannon underwater without getting the gun powder and fuse wet.

Sharks are born color blind, therefore the Chief Shark wouldn't even know what yellow looks like.

When the main characters are about to meet Pingo, they meet two soldiers guarding his building. Don wonders if they are toy soldiers which the Atlantean captain says they are and that they have rescued toys that fall to Atlantis during the crossing, and many more big toys are seen shortly later. However it makes no sense why someone would have toys as big as people or how they could of been lost.

At the start of the film the main characters are in a Bathysphere, but the film is set in 1915 and the Bathysphere was not used until 1930.

Many times through the film the characters voices don't match their mouth movements.

After watching the magic monitor on what became of the evil rats. There was no sound when the Atlantheans applaud.

A large portion of the plot revolves around the main characters being unable to leave Atlantis because they'll know of its existence. However during the main climax of the film it is revealed that the Atlanteans have the power to erase memories, meaning their detainment in Atlantis is entirely pointless.

It was clearly stated that all screw drivers are banned from Atlantis yet we see Screwy who is clearly a talking screw driver. She is also shown to be close friends to Pingo the toy fish, despite him previously showcasing an incredibly strong fear of them.

In the original film, Top Connors is a grandfather mouse living in New York who tells the main story in a flashback to his grandchildren. However, at the end of this film, he is stranded on an island for the rest of his life and will forever remain young, making the film incompatible with the first movie as Connors would never be able to go home to New York and have grandchildren in the first place.

When Oddy and Pingo get ready to move the Titanic to the shore of the forgotten island, a huge manta ray character is introduced to help them. She could of been used to battle the sharks and rats but strangely didn't.

Razor Teeth says he hates the color yellow, yet the suit he wears has a bit of yellow on it.

Maltravers is constantly shown to be a generic vindictive villain, but when he thinks his butler has turned up to work in a vest and his underwear he doesn't react aggressively in any way, only telling him he can't wear anything he wants just because they're on vacation.

When Razor Teeth is telling his squid henchman to send his Morse code letter, he starts it off with "to the right honorable..." but the squid seems to press the "O", "I" and "A" first.

When the main characters are in the Bathysphere surrounded by sharks, Connors says "there's something definitely wrong here and we're in trouble, trust me!" but he seems to be very happy and jolly when saying what is going on which makes no sense.