The World's Most Powerful Computer is a minor alter ego of Calvin's. He appeared in a single story arc (7/6 through 7/7 1993) as an upside-down cardboard box with drawn-on features, which claimed to have the answer to any question it might be asked.
The box for The World's Most Powerful Computer was smaller than the one used in most of Calvin's inventions. Calvin had drawn unfocused eyes and a squarish mouth onto the computer's "face", and on its side had written some nondescript text and drawn two buttons.