Weepy is a demon that lives in the mysterious Puzzle Tower, in a far away part of Rainbow World (a place Super Bust-A-Move 2 suggests has never been explored by anyone before, which is clearly an exaggeration). He is the protector and guardian of the Tower, and his purpose is to ward off travelers or invaders looking to defeat the Tower for glory, fame or other wishes. As his name suggests, Weepy is a very depressed character that lacks self confidence and has no faith in himself or his abilities as a Puzzle Bobble master, despite being one. Weepy has a split personality and is in fact one half of a character, his alter ego being the far more positive and self-confident Smiley.
The origins of Weepy are pretty much unknown, and most of his past his shrouded in mystery. The only thing we really know about him is that he protects PUZZLE TOWER, a tall structure filled with puzzle bobbling challenges ranging from puzzle to VS, from anybody who decides to invade it and face these challenges inside. Puzzle Tower is a equally shrouded in mystery, but we do know that it has been challenged before, but by who, for what and what the outcome was is completely unknown.
Weepy appears as a demon that lacks self-confidence and is very depressed all the time. He feels that he is not strong, nor skilled enough to defend the tower, despite the fact that he really is. He seems to also have a form of social phobia, usually running away from confrontation with challengers of the tower and only fights when backed into a corner and is given little other option. This being said however, he can be triggered into switching into his bi-polar based alter-ego, Smiley, who is the polar opposite of Weepy, being fully self-confident, strong, skilled and constantly happy and in no way afraid of confrontation with tower challengers. (due to being aware of his ability now). He switches to Smiley when backed into a corner at the top of the Puzzle Tower at the end of Super Bust-A-Move 2's story mode.