[TOMT] [movie] a cartoon movie with sort of a comic book aesthetic in the adventure genre from the late 90s to mid-2000s

I saw this film on television when I was about 7 or 8 during the mid 2000s (so the film was definitely made before that). So far, I couldn't find it anywhere on the internet (I've tried movie search engines, forums, etc.) and I would really like to know the title so I can watch it again because of nostalgia and stuff. It was an adventure story kind of cartoon with a lot of comic book style visuals (panels as transitions, etc.). As far as the story goes, I don't remember a lot, only that it was centered around this group of kids (with one comedic relief adult/elderly guy) who were uncovering some sort of mystery (it takes place in modern day as I can recall one of the kids having a gameboy like device). One of the characters was this orphaned girl who I think was a princess of some sort. Her guardian however wants the throne that the girl would be inheriting and uses hypnosis to manipulate her. These two are introduced in a scene on a ship (I think, I'm absolutely not sure) where the kids first meet the princess but her guardian doesn't like her talking to other kids so he hypnotizes her to make her go to her room. The kids find her guardian very shady and go investigate after those two. They find her inside a (I think) horse-drawn carriage and try to get her out of there but they notice she's still under the spell. In the end, the heroes manage to interrupt some kind of ceremony where the hypnotized princess is in the process of giving the guardian some kind of artifact (which I assume gives him the 'throne') and break the spell she's under. The guardian is busted and 'all is good again'. I hope someone can help me with the title of the film.

EDIT: The main characters are all human. IIRC besides pets, there were no animals in the film.