The Sweetheart Sister ponies first appeared in Year 7 of the My Little Pony line and returned with different versions in all of the remaining years.
The Sweetheart Sister ponies were a teenage or young adult size, they were larger than the baby or Flutter ponies, but had a smaller, sleeker body than the adult ponies. They had painted-on eyeshadow and most versions had a plastic flower-shaped earring in each ear. The earrings could not be removed, so this made them prone to breaking. The Year 7 Sweetheart Sister ponies came with a lacy ribbon to tie in their hair.
There were two sets of Sweetheart Sister ponies released in Year 8 as well as a mail order pony named Goldilocks. The Glitter Sweetheart Sister ponies had tinsel in their hair and glittery symbols that covered the sides of their bodies, similar to the Twice As Fancy ponies. The Prom Queen Sweetheart Sister ponies came with perfume and a lacy ruffle that could be worn by the pony as a skirt or by her human friend as a hair scrunchy. This set had hair with tight curls.
Year 9 brought the Pretty Ponies, these ponies did not have earrings and were very basic with none of the frills of earlier sets.
There were two sets released in Year 10, these sets did not have earrings. One set was the Sweet Kisses ponies. They had tinsel in their hair and lipstick lips that could disappear and reappear. The other set was the Sundazzle ponies, which had manes that changed color in the sun, similar to the Sunshine ponies. The Sundazzle ponies had crimped hair.