Glowbo

Those Mysterious Little Glowbos
Glowbos are small creatures that appear to just be a head with feet and big ears, big eyes, and no torso. Mumbo Jumbo and Humba Wumba both require you to give them one Glowbo in every world before they will help you. Glowbos usually aren't hidden very well in the worlds, and they make little giggling noises when you get near them, giving you a hint as to where they are, like Jinjos do. They are supposedly magical, and yet, they don't attempt much self defense when you try to grab them. There is one giant Glowbo called the Mega Glowbo, that is needed to get Dragon Kazooie in the game, but the only difference is that it is about 3 times bigger and 2 times faster. Mumbo requires Glowbos to use his magic spells, and Wumba requires Glowbos to transform Banjo and Kazooie into stuff.

Trivia

 * If you watch closely, the first time you use Mumbo's spells or Wumba's pool after giving them a Glowbo, the Glowbo will hop out of the pool or out of Mumbo's bag and disappear before the cutscene is complete. Yet, they only need the one Glowbo and even though it runs off, they can use their magic as much as they want for the rest of the game.
 * One wonders why Mumbo and Wumba need help finding the Glowbos in certain worlds, in Mayahem Temple, the Glowbos are found inside Mumbo's Skull and inside Wumba's Wigwam.