Fair for Its Day: Back when the franchise was still huge, it was actually somewhat praised for its large cast of diverse (at least on the surface) characters.
Older Than the Demographic: Controversially so. The toys feature arguably sexualized teens but are aimed at preteens. It's been criticized for being age-inappropriate. As a result, the characters were eventually retooled to dress more conservatively and put more emphasis on the Be Yourself aesop rather than the fashion and partying.
Overshadowed by Controversy: Outside of the target demographic, the dolls are best known for the controversy they caused about being "ultra-sexualized".
Uncanny Valley: Many comments and jokes have been made about how creepy and inhuman the Bratz look.
Crosses the Line Twice: A clearly distraught radio caller tells Kirstee that their cat has recently died. What does Kirstee say? "Get a new one." In the most non-caring way possible. How blunt she says it in response to a pet's death is just offputtingly hysterical.
Love to Hate: The antics of Burdine and the Tweevil Twins are so over-the-top that you can't help but watch the show merely because of them.
Nightmare Fuel: In A Cinderella Story, Burdine murders Cinderellas father by force-feeding him too many carbs. The music and the amount of food he is fed, as well as his death, can be quite disturbing.
Uncanny Valley: The CGI has not aged well, even for 2005 standards. The character designs are based off of the dolls, and come out looking quite disturbing.
Audience-Alienating Premise: Most of the things associated with the Rock Angelz movie and doll-line, the CD included some pretty great songs (Nobody's Girl and So Good) and the video game (also mentioned below).
Continuity Lock-Out: If you want to watch any of the videos, you better start out with the first two (Rock Angelz and Genie Magic) as those two have callbacks to later events and Genie has a sequel called Desert Jewelz. The only ones you don't need to worry are the 2D ones and the Babyz (Super Babyz and Saves Christmas) and Kidz spinoffs. The former because they're a different continuity and the latter, while still the same canon as the CGI ones, don't really have a strong continuity.
The Problem with Licensed Games: A series of video games based around Bratz were eventually introduced. All of these games used the exact same engine and gameplay, had painfully forced tutorials, poor graphics and terrible controls.
Squick: One of the extra clothes one could buy for the Babyz was a small bikini. Another one had fishnet stockings.
Uncanny Valley: A large possible factor in why the direct-to-DVD movies and TV show never got very popular: the characters look downright horrifying in CGI.