Plot hole: When Charlotte kissed Naveen at the end, she should've turned into a frog as well because she was no longer a princess.
Suggested correction: When ordinary people kiss a frog, they don't transform into anything. (Perhaps they die from infection after a few days.) Charlotte was just an ordinary person. Tiana was chosen. She wished upon the star. Naveen and the consequences of kissing Naveen were a result of Tiana's wish.
Suggested correction: How? She was no longer a princess.
Tiana turned into a frog because she kissed Naveen without being a princess, so Charlotte should have, too.
Plot hole: Mr. Cranston asks Denise to be the accompanist for the school's production of "Chicago". This is an error. In the year 2009, in which the film is set, this would be impossible since the licensing company which has the theatrical rights for "Chicago" restricts the show from being produced (even by amateur groups and schools) anywhere in the greater New York area while there is an open-ended production running on Broadway.