Gruntilda Winkybunion, often referred to as Grunty, is the main antagonist of the Banjo-Kazooie series. She is a witch who constantly rhymes.
In Banjo-Kazooie, Gruntilda kidnaps Banjo's younger sister, Tooty, in an attempt to switch looks with her so that she will be beautiful and Tooty will be ugly. She remains at the top of the tower for most of the game, taunting and insulting Banjo and Kazooie along the way, until finally, they reach Gruntilda's Furnace of Fun, a quiz show in which she'll give back Tooty if they win, or drop them in boiling lava if they lose. They win, though, and Gruntilda runs off. Later, Banjo and Kazooie follow her up to the very top of her lair where they have their final battle. Through a huge climax and with the help of the Jinjos, they knock Gruntilda off the tower and she falls to the ground, where upon she's immediately buried under a giant boulder. As her loyal minion attempts to move the boulder, she swears her revenge in Banjo-Tooie.
At the beginning cutscene of Banjo-Tooie, it's shown that Grunty's minion, Klungo is trying to move the boulder to free Gruntilda.