It is unspecified when exactly Kelly & Donna met, though plausible that they met as high school freshman. It is seen that they were close friends before the series till about 1991, and later on they become best friends, and become roommates in college.
Jennie Garth and Tori Spelling are best friends in real life.
Donna and Kelly both owned BMW 325i Convertibles. Donna had a beige one, and Kelly had a red one.