I edited the touchscreen Neko program to include Marisa sprites based on her sprites from “Patchcon: Defend the Library!”, except in monochrome. She can also be controlled by serial port if connected through USB: send a header byte of 255 to the Arduino, followed by the X and Y coordinates, and she will move there (assuming the previous command was a valid one). This allows her to also be controlled by, say, Ustream/IRC chat commands.
Source code and bitmaps can be found here.
Update: Had an interactive stream on Ustream where viewers could type “!mari” followed by two integers, and she would move to the coordinate (unless it’s too large or small, then she moves to wherever she can). Here‘s a recording of the stream; cooler stuff happens at about 13 mins onward (fire and snow effects). It doesn’t record the chat messages though, but they were definitely there.