After Lilo gets a photograph of her and all of her Ohana (including the experiments) she puts it into the book which contains the pictures of all the experiments. The other photographs appear to be normal, but earlier on in the movie, Leroy tore an X in each picture as he caught the experiments.
When Stitch is giving his pep talk to the Experiments before the Leroy and Experiment battle, Stitch's collar from Lilo is missing. It is seen around his neck in the next scene.
The closed captions on the DVD misspell Mertle's name as "Myrtle".
When Lilo and Reuben arrive at Galactic Headquarters, Lilo says in surprise "They're letting us land!" But since they do not yet know that Hamsterviel has taken over, and the last time she was at headquarters, she was hailed as a hero, there is no reason for her to be surprised. She would expect to be welcomed.
During the battle scene when all the Leroys begin to over power the other experiments, one of them fires at Clyde (one of the criminal experiments couple (Bonnie and Clyde)) and knocks him over, Bonnie wrongly calls him by her name instead of his when she goes to attend to him.
Tickle-Tummy, an experiment who was previously seen in the TV series, was accidentally left out of the list of experiments seen in the closing credits. Some fans believed that she was the unseen Experiment 628 until executive producer Jess Winfield later stated that she was mistakenly forgotten. In the credits, her experiment number (275) was taken by "Mamf", who never appeared in the franchise.
One of Mertle's friends states that Lilo was not at hula class. In the second film, Lilo was suspended from attending hula class due to Stitch malfunctioning during the dress rehearsal.