Clinker

Clinkers are large, brown, ameobal creatures of questionable compostion that block ventilation grates in Clinker's Cavern of Grunty Industries. Banjo and Kazooie are tasked with clearing twenty of them out before the area becomes toxic. (Clinkers can still be cleared after the air is infected, but it's a risky maneuver.)

The Clinkers are named after the British slang "clinker", which is a deposit of rust & grime that tends to form on various metallic surfaces. However, it is unknown if the Clinkers in Banjo-tooie are comprised of said materials or not...