Bratzillaz is trying its best to cash in on Monster High, trying so hard they're copying even the marketing. Judging by the low view counts of the webisodes though, it's not exactly edging in on MH quite yet...
Screwed by the Lawyers: The courts found the toy line was being worked on by Mattel before the creator left the company, so Mattel won a suit to discontinue the line. According to some fans, this is evidence that Barbie is jealous of the Bratz. Speaking to those fans—Judge Alex Kozinski, who granted MGA the appeal, seemed to agree that there was some "jealousy" involved in the case, saying, "America thrives on competition; Barbie, the all‐American girl, will too."(See here) and (here).
The Other Darrin: Cinégroupe produced the first direct-to-video movie, Starrin' and Stylin', which featured a different (uncredited) cast from the TV series which was produced by Fox and Lionsgate. For the TV show's second season, Fox stopped producing the series, so Lionsgate took over, replacing the entire cast.
Cloe's actress (Skyler Shaye) was 21 at the time the movie was released, playing a senior high school girl. Also Anneliese van der Pol, who was 23 years old when she played Avery.
Inverted with then 15-year-old Nathalie Ramos playing senior Yasmin (unless she's so smart she jumped three grades).
Franchise Killer: Downplayed. The film bombing is often believed to be the main cause of the toyline fading into relative obscurity.
Genre-Killer: This movie basically killed off the idea of theatrical films based off dolls, with any further films based on them going direct-to-video. This may also have been why cinemas were weary about showing Kit Kittredge: An American Girl the next year, even though it got good reviews from critics.