Wikipedia
Ukagaka
Ukagaka (伺か), also known as Nanika (何か), Sakura (さくら), Nin'i-tan (任意たん) or Nise-Haruna (偽春菜), is a catch-all term for Japanese software which shares a single format and function: to provide a pair of mascot characters for the user’s computer desktop. These mascot characters can perform some useful functions such as checking e-mail or adjusting the clock of the computer, but are most popular as an aesthetic add-on, which “says” weird things.
Characters are typically cute anime girls of original design as seen in the sample screenshot, accompanied by a small monster or pet of some sort. However, a variety of other subjects exist on the sidelines, from video game characters to 2channel memes to humorous depictions of Hitler.