She's the mascot of the character designer for Disgaea, Takehito Harada. She's only in games that he did the character designs for. She's also cameoed in Pani Poni Dash, but I don't know the story behind how she got there.
unicogirl said: must be a common manga pose cause i swear i saw this in Chobits.
really I think poses will be re-used cause there are only so many .__. but yeah most of the time you can find this pose rotated or knees closer to the chest.