Napper

"Grunty's gold how it shone, she'll be mad now it's gone!"

- Napper Napper is a large, green ghost who inhabits Mad Monster Mansion.

Banjo-Kazooie
In Banjo-Kazooie, Napper is located in Mad Monster Mansion's Dining Room and was entrusted by Gruntilda to safeguard a Jiggy from Banjo and Kazooie. He is transparent while he is asleep, but becomes more opaque while he is awake. Napper is a light sleeper as even a slight floorboard creak awakens him. Because of this, Banjo and Kazooie must take an alternate route into the mansion by entering from a chimney on its roof. After this, they must hop from the fireplace to the chairs positioned in front of Napper and onto the table, where they must walk through Napper to obtain its Jiggy. By doing so, Napper wakes up and flees in fear of Gruntilda's wrath.

Banjo-Kazooie: Nuts & Bolts
In Banjo-Kazooie: Nuts & Bolts, Napper is mentioned by an Information Speaker in the Mad Monster Mansion exhibit's description, where he is described as a "dozing ghost."

Trivia

 * According to Grant Kirkhope, his voice is a slower variant of Banjo's voice.