Other mistake: Charlotte's dad buys a newspaper in the beginning of the film. The same two paragraphs about Prince Naveen are repeated all over the front page, including under the headline 'Annual Goosenhoper State Gumbo Faire Is Smashing Success.' (00:08:45)
Other mistake: When the old woman is cooking gumbo in a large bathtub, it's shown boiling and really hot. Yet the two frogs can sit right on the rim of the bathtub inches above the boiling food in a non insulated tub without getting burned or even hot.
Answer: Naveen told Tiana about his plan to marry Lottie once they arrived in the swamp. After revealing that he's been cut off by his parents, he explains that he plans to regain his wealth by marrying her so that he'll inherit her father's prosperity.