The story so far...
The story starts 2 years after Banjo and Kazooie defeated Gruntilda adn sent her to her prison under the boulder. Banjo, Kazooie, Mummbo and Bottles are playing poker. Just when Mumbo was about to win, there is loud noise outside. Everyone but Mumbo is too scared to investigate, so Mumbo goes outside.
It seems that the source of the noise is a giant drill that was being used to break the giant boulder that was over Gruntilda. The drill was being controlled by Klungo and Gruntilda's 2 evil sisters(no names as of yet) and they were determined to get Grunty free. As soon as the boulder was gone, Gruntilda climbed out of the crater. It seems that being under that boulder for 2 years has reduced Gruntilda to nothing but a walking skeleton. Grunty, her sisters, and Klunko were just about to head to the Isle o' Hags in order to cure Gruntilda, when Gruntilda spotted Mumbo. She quickly gave chase and Mumbo ran towards Banjo's house.
Once Mumbo got inside Banjo's house, he told the rest of what events just took place. Then he, Banjo, and Kazooie fled outside, but Bottles stayed inside thinking that it was a trick. As soon as they got outside, Gruntilda blew up Banjo's house with a fireball, went and broke the bridge to her lair, then her and the rest of her cronies fled towards the Isle o' Hags.
Then all of the sudden, Bottles emerges from the wrekage, falls, and dies. Then Kazooie coldly remarks, "Well, at least he was the least liked character of the last game."