Bonus room

A Bonus Area (also known as a Bonus Room or Bonus Level) is a hidden area in the Donkey Kong series of games, particularly the Donkey Kong Country and Donkey Kong Land games.

Bonus Areas are usually revealed by finding either a secret passage, or by jumping into a Bonus Barrel. In Bonus Areas, there's almost always a prize of some nature. In games following Donkey Kong Country, the there is always a goal of some sort in the Bonus Areas that the Kongs need to accomplish, and a useful reward for meeting it.

Donkey Kong Country
In Donkey Kong Country and Donkey Kong Land, Bonus Areas are entered by either breaking open certain walls with Barrels to reveal secret passages, or by jumping in certain Auto-Fire Barrels. Levels can have anywhere from zero to five Bonus Areas, but most levels have around two.

There are several different kinds of Bonus Areas. In one, Donkey and Diddy Kong can explore the area at their leasure, and collect any treasures they find. In others, they have to play minigames of sorts to collect prizes, such as lining up prizes in the correct order, spelling words, jumping on Klaptraps in succession, among others.

There are also Bonus Areas that can only be reached by collecting three Animal Tokens of any animal. Upon collection of the third token, the Kongs will be warped to a special Bonus Area, where they'll play as the animal whose tokens they had collected. The goal of these Bonus Areas is to collect as many Mini Animal Tokens as possible before time ran out.

Donkey Kong Country 2: Diddy's Kong Quest
In Donkey Kong Country 2: Diddy's Kong Quest, Bonus Areas are entered much like they were in Donkey Kong Country, except that the Auto-Fire Barrels that led to Bonus Areas have been replaced with Bonus Barrels. All levels have between one to three Bonus Areas. Also, the Bonus Areas now have time-based challenges to complete, with Kremkoins as prizes. In the Lost World, DK Coins were the prizes instead.

Find the Kremkoin! – Diddy and Dixie have to make it to the end of the Bonus Area before the time limit expires.

Destroy Them All! – Diddy and Dixie have to defeat all the enemies to make the Kremkoin appear.

Collect the Stars! – Diddy and Dixie must collect all the Stars in the Bonus Area to make the Kremkoin appear. In a few cases, there are more Stars than the ammount required.

Donkey Kong Country 3: Dixie Kong's Double Trouble!
In Donkey Kong Country 3: Dixie Kong's Double Trouble!, Bonus Ares work similar to the way they did in Donkey Kong Country 2, except now they're always entered through Bonus Barrels, and never by secret passages. There are also always two per level, except in Krematoa, where the ammount varies between zero and three. Lastly instead of Kremcoins, Dixie and Kiddy Kong collect Bonus Coins in the Bonus Areas.

Find the Coin! – Identical concept to Find the Kremkoin!.

Bash the Baddies! – Identical concept to Destroy Them All!.

Collect __ Stars! – Same concept as Collect the Stars, except that the ammount of Stars that the Kongs need to collect is displayed when the Kongs enter the Bonus Area.

Collect 15 Bananas! – Dixie and Kiddy must collect fifteen Green Bananas within the time limit to make the Bonus Coin appear.