Princess Serenity as seen in the manga. Unlike in the anime, Serenity is almost always pictured with silver hair in this version.
Princess Serenity (プリンセス・セレニティ Purinsesu Sereniti) lived in the Moon Kingdom during the age of the Silver Millennium as the daughter of Queen Serenity, who ruled the Silver Millennium and watched over the Earth. Princess Serenity's guardians and closest friends were Sailor Mercury, Sailor Mars, Sailor Jupiter, and Sailor Venus, who were princesses of their own respective planets, but lived on the moon with her at times. the moon princess is NICE
Princess Serenity often explored Earth to see real greenery, even though forbidden to do so.On one of her visits, she met the crown prince of the Earth, Endymion, and they fell in love.
During the attack which caused the Moon Kingdom's downfall, Prince Endymion died protecting Serenity. In the manga, she committed suicide out of grief, while in the anime Queen Metalia killed both of them. Serenity's mother, the Queen, was able to seal away the evil which had inspired the attack, but everyone involved was killed. Before her own death, the Queen used the Silver Crystal to give her daughter and others another chance at life, hoping in particular that, this time, Serenity and Endymion could find happiness together. In the live-action series, it was Princess Serenity herself who destroyed the Moon Kingdom, after Endymion was killed during the war to keep the two apart.
Eventually, Serenity reincarnates as Usagi Tsukino in the 20th century. Usagi occasionally takes the form of Princess Serenity during the meta-series, often at climactic moments when more strength is needed than Sailor Moon can access. Usagi discovers her identity as a princess in Act 9 of the manga, Episode 34 of the anime, and Act 25 of the live-action series.
Whereas Takeuchi draws Usagi with white, yellow, and even pink hair and blue eyes, in the manga Serenity almost always has white hair and blue eyes. In the anime, both characters are always blond. In the live-action series, Serenity has black hair and brown eyes, just like Usagi, and she wears her hair straight down rather than in pigtails. This emphasizes the ambiguity of her identity before the storyline reveals her as Usagi.
At climactic moments, Usagi as Serenity sometimes gains a pair of functioning angelic wings. She does this during the final battles of SuperS, after she jumps off a tower to save Chibiusa and the two of them collide with Pegasus while falling. It also happens in Sailor Stars during the fight with the fully-possessed Galaxia when she grabs the Sword of Sealing. It remains unclear if this power comes from her past life, if it belongs to Usagi herself, or if it came from Pegasus and the Sword of Sealing.
The first two series dubbed by DiC refer to Princess Serenity as Princess Serena (although the original name is used at least once, to emphasize the similarity between Princess and Neo-Queen Serenity). In the last two series, dubbed by Cloverway, the name Serenity is used.