Clinker

Clinkers are large, brown, amoeba-like creatures of questionable composition that block the ventilation grates in Clinker's Cavern of Grunty Industries. Banjo and Kazooie are tasked with clearing twenty of them out in a limited amount of time before the area becomes toxic. (Clinkers can still be cleared after the air is infected but it is a risky and dangerous maneuver.) Clinkers are easily located due to the... ahem... "distinct" sound they constantly make.

If Banjo inputs the cheat "HONEYKING" in the Code Chamber of Mayahem Temple, the Clinkers cannot harm him even after the timer has expired; he will just have to deal with the toxic, greenish gas.

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