First of all what is BMO? Simply speaking it is a living game console plus music player, camera, alarm clock and everything you can think off. Fileark wanted to build something similar to original one so he started an Arduino based BMO. Central brain if it is Arduino Pro Mini with Nokia 3310 LCD screen.
He placed all components in to nice custom 3D printed box, that mimics original BMO. Currently it is equipped with WTV020-SD Audio player to play different loaded sounds (amplifier and couple speakers are also included). 2Y0A21 Sharp distance sensor and ADXL335 accelerometer gives some interactivity while playing around. There are 7 push buttons for selecting things and playing games. As you can see this is a platform which can be further expanded with sensors and functions. Eventually you may run out of memory or processing speed. So for project like this probably it is better to start with faster processor or board like Raspberry Pi. You can put lots of stuff in it and then see kids trying to explore its capabilities.