Totally Hair Barbie was the bestselling Barbie line, but if I had to guess what the most well-known Barbie line is, I am fairly sure that would be Malibu Barbie.
Malibu Barbie first debuted in 1971. Not only that, but she also had a whole series of pals - Malibu Christie, Malibu PJ and Malibu Francie.
The line was released over the course of a few years, with different variations on packaging and oufits.
This became such an iconic part of the line that it saw multiple celebratory and anniversary rereleases over time.
Interestingly - or maybe this is only interesting to me, I'm not sure - this old Sears ad for the The Sun Set Malibu Barbie range advertises that the dolls originally went for under $2 apiece.
Malibu Barbie has become such an iconic part of the Barbie history that a lot of parodies of Barbie will specifically refer to her. For example, the famous Barbie parody from The Simpsons was Malibu Stacy.
Even though Malibu Stacy appears to be the name of the whole collection in this case, not just a single doll in an overarching "Stacy" line.