Princess

Princess was a pony owned by Lisa.

History
Homer got it for her after he got a drink at Moe's when he was supposed to get her a saxophone reed. After Lisa got her, Homer and Marge suffered as supplies for the pony were expensive. Soon, Lisa realized that Princess was a strain on the family financially, so she gave her up.

When Lisa returned to Springfield from Canada, she went past Princess and said that she missed the pony she only had for a week.