Which Lego theme introduced the mini-doll figure?

LEGO Friends introduced the mini-doll figure.

When LEGO Friends launched in 2012, it brought a new character format to the LEGO System: the mini-doll. Mini-dolls are broadly compatible with LEGO environments and accessories, but they have slimmer bodies, more detailed proportions and a more stylised, realistic appearance than the classic blocky minifigure. The design was created for detailed character-based role-play while preserving the building system’s basic play possibilities.

The original Friends world centred on five characters—Andrea, Emma, Mia, Olivia and Stephanie—and their lives in Heartlake City. The theme used those characters to support stories involving friendship, school, homes, animals, hobbies and community activities.

A common mix-up is treating “mini-doll” as simply another name for a minifigure. LEGO uses the terms for distinct figure designs. Later themes, including some licensed and fantasy lines, also used mini-dolls, but Friends is the theme credited with introducing this character type to the modern LEGO range.