Kagamine Rin

Kagamine Rin is one half of the second installment of Vocaloid2, also known as Kagamine Rin/Len. She, as well as Len, were created by Crypton Future Media as singing synthesizer application software that could be used to cover music as well as create original songs. Their shared software included two separate voice banks, using the same singer's voice samples, because there was demand for another male Vocaloid while they were still creating Rin. Because of this, Rin and Len are considered both to be mirror images and twins, but, due to the user-created nature of the characters in which the fans decide on their personalities and other information, Crypton backpedaled on marketing them explicitly as twins as was originally intended. It is, however, official that she and Len are 14 years old in regards to human age.
Several months after release, an update was created for the Kagamine software, improving the vocal quality of the two voice banks. However, their voice banks remain only Japanese, unlike some later releases.
Before the Kagamine product was released, however, there was a debate between the fan community on what her signature item would be (such as Hatsune Miku's signature leek item; Kagamine Len wasn't yet announced at this time). All of the suggestions didn't have a very strong impact, including an orange, a banana, or an onion—although, later, Rin would be given an orange and a yellow onion, while Len would get the banana.
However, a video emerged on Nico Nico Douga titled "Excuse me… I want to make a reservation of Kagamine Rin…" In the video, the Hatsune Miku software was used to have the character Hatsune Miku give a small speech, introducing herself, and then bringing up the topic of Rin.
A loose translation of what she said would be, "Miku has the leek, doesn't she? In short, a vegetable! Therefore, I think that Rin… should have a road roller! How's that?" Because of the unexpected proposal of the video, the idea soon caught on, and the Road Roller became a character item for both Kagamine twins. This video was also the history of the Road Roller's signature sound effect, "WRYYYYYYN", as Miku also suggested, as it sounds like Rin's name. The entire idea was based on the character Dio's (of Jojo's Bizarre Adventure) infamous time-stopping attack.