Information on the Cameo
Mumbo Jumbo is a supporting protagonist in the Banjo-Kazooie video games. He is a shaman with a skull for a head who in the first game can transform the heroes into various animals to perform special tasks and in the second game can be directly played as in brief segments to go out and perform scenery-altering spells. His previous role of animal transformations is here given instead to Humba Wumba, a more human and attractive female shaman who is considered Mumbo's rival.
Early promotional material stated that Mumbo Jumbo was once human and was the magical mentor of the witch Gruntilda, who betrayed him and cursed him with his current form, and now Mumbo wants to help kill her which would restore him. However, this is never mentioned in the games, and furthermore Grunty is portrayed as completely immortal, with reducing her to the closest possible states to death having no effect on Mumbo.
In the "Game Over" screen of Banjo-Kazooie, Mumbo appears in Gruntilda's Lair with flowers after her success in stealing Tooty's beauty, falling in love with her new form; this is the context that his MERB appearance is based on.
Eekum bokum, New-U is very good!
Meet with Mumbo at my magic-making mountain, Grunty should.