A cute little guy, Bubbi was made by the Great Beings as a "prototype" for Matoran. Most of the GBs were displeased with the prototype. But one of them kept it as a domestic pet and named it Bubbi. Though he may be capable of it, Bubbi never learned to speak. He just makes Snarf-like sounds(see link below). In the events of the Shattering, Bubbi was lost and ended up on the fragment known as Bota Magna.
More recently on the joined Spherus Magna, he met Ferix and began to accompany him on his travels.
Bubbi is fairly articulated in the arms and has a lot of movement in the head/neck. He sounds like this: http://www.youtube.com/watch?v=EpvlAEPiXcI&feature=related