My Little Pony is an entertainment franchise developed by Hasbro which is marketed primarily to girls. Started as plastic pony toys developed by Bonnie Zacherle, Charles Muenchinger and Steve D'Aguanno which was produced since 1983, the ponies feature colorful bodies and manes and a unique symbol on one or both sides of their flanks, referred to in the two most recent generations as "cutie marks." My Little Pony was revamped at least four times with new and more modern looks to appeal to a new market.
Following the original My Pretty Pony toy, introduced in 1981, My Little Pony was launched in 1983 and the line became popular during the 1980s. The original toy line ran from 1983 to 1995 (1992 in the US), and inspired animated specials, an animated feature length film, and four animated television series.
Source: Wikipedia, "My Little Pony", available under the CC-BY-SA License.
The My Little Pony product line has since expanded to video and video games, among many other media types.