Toxic waste

Toxic Waste (also called Acid) is an uncommon obstacle appearing in the Donkey Kong franchise.

Donkey Kong Country 2: Diddy's Kong Quest / Donkey Kong Land 2
Toxic waste makes its first appearance in the level Toxic Tower in the game Donkey Kong Country 2: Diddy's Kong Quest. In this level, the player(s) must climb a tower slowly filling with toxic waste, while being transformed into multiple Animal Friends. If a player touches the toxic waste, they will instantly lose a life.

The level Toxic Tower is later revisited in Donkey Kong Country 2: Diddy's Kong Quest's semi-sequel, Donkey Kong Land 2, where toxic waste reappears functioning the same as it did in Donkey Kong Country 2: Diddy's Kong Quest.

In the Game Boy Advance remake of Donkey Kong Country 2: Diddy's Kong Quest a Funky's Flights level called Toxic Kongstruction has the Kongs swerving around in their Gyrocopter while collecting pieces of a golden statue of Donkey Kong. In this level, several pieces of the statue are submerged in toxic waste thus requiring the player to shoot the buttons on the walls of the stage in order to temporarily lower the toxic waste, allowing the player to collect the pieces of the statue until the toxic waste rises back up. If the player touches the toxic waste, the Gyrocopter will explode.

Donkey Kong 64
In Donkey Kong 64, pools of toxic waste can be found in the level Creepy Castle.