Bonus Stages, also referred as Mini Games, are extra, optional mini-games in the games in the Sonic the Hedgehog series, where the player usually enters a different type of Stage with a different gameplay style. Bonus Stages are usually meant as a place where the player can collect Rings, points, extra lives or other items when passing through a zone. In each game, there's different way to enter Bonus Stages as such being transported after collecting certain amount of Rings, finding hidden Giant Rings or after passing through the regular Zone. Bonus Stages and their gameplay styles vary between each games, as they have featured many different gimmicks such as gumballs, slot machines and other types of mini-games.
Bonus Stages are not to be confused with Special Stages, as the objective of the Special Stages is that the player collects something in order to obtain a Chaos Emeralds. Regardless, some of the Special Stages have retrained the same role as Bonus Stages in several games.
Sonic the Hedgehog Spinball
There are four different Bonus Stages in Sonic the Hedgehog Spinball, all of which take place inside a regular pinball cabinet. In this game, the player can play three Bonus Stages after passing through the regular levels, as the fourth level only becomes playable if the player has collect all the Rings from the three previous levels. When playing in the Bonus Stages, Sonic himself can be seen playing the pinball table in the reflection of the windows in the background.
Each Bonus Stage has its own requirements for gathering more points to the total score. When playing, the player has three pinball balls to use during the Bonus Stage. Completing them will rewarded the player with "Rising Jackpot".
In the 8-bit version of Sonic the Hedgehog Spinball, there are different three different Bonus Stages which the player can enter in the same manner as in the 16-bit counterpart game. Here, however, Sonic appears the pinball sections and is able to find treasure boxes with points, Rings, extra lives and Continues.
Sonic the Hedgehog 3 & Knuckles
Sonic the Hedgehog 3 and its add-on continuation Sonic & Knuckles have three different Bonus Stages, which the player can enter via a Star Post when having a certain number of Rings in hand. While Sonic the Hedgehog 3 only features one type of Bonus Stage and Sonic & Knuckles features two, the locked-on version of the game, Sonic the Hedgehog 3 & Knuckles features all three Bonus Stages. Each Bonus Stage's gameplay and purpose are different. Sometimes, if this stage is accessed by a glitch, rather than saying "Bonus stage", the title card will say "Dolius Stage" instead.
In Sonic Labyrinth, a hidden Bonus Stage can be entered by finding the closed door with "BONUS" mark on it in Labyrinth of the Sea. The player has to enter a cannon to be launched into the direction where the door is located. After entering the Bonus Stage, the player can collect a huge amount of Rings within 30 seconds, where each Ring adds 25 Rings to the score. After clearing the Bonus Stage, the player obtains the sixth Chaos Emerald and can clear the game with the good ending.
In Knuckles' Chaotix, there are hidden Giant Rings set around in each Stage which can transport the player into the Bonus Stage if he/she possesses 20 Rings. Here, the player gets transported into a different dimension that serve as the Bonus Stage, which Combi partner does not appear in. In these Bonus Stages, the player falls down an endless void where numerous power-up boxes float around. By touching certain power-up boxes, the player can collect Rings and points. If running out of Rings or hitting an Exit box, however, the player is send out of the Bonus Stage.
Sonic Advance 3
In Sonic Advance 3, there are two types of mini games available, which the player can participate in by finding Transporters within each Zone Map. In the first mini-game, the player has to press one of the five switches that lights up on a large capsule as quickly as possible to earn as many points as possible, and in the second mini-game, the player has to destroy all enemies within the area. Depending on how long it takes the player to complete these mini-games, the player is rewarded with a certain number of extra lives.
- On a single screenshot of 1992 Sega Summer Catalogue it is shown that there was originally meant to be labyrinthine levels in Sonic the Hedgehog CD, which could possibly be scraped Bonus Stages. These levels are somewhat reminiscent of Special Stages from the original Sonic the Hedgehog.
- Certain Special Stages in Sonic the Hedgehog series do not focus on finding Chaos Emeralds, but rather to collect points, Rings, extra lives and Continues like in the Bonus Stage. Few examples include from the 8-bit version of Sonic the Hedgehog and Sonic Blast (if the player enters the Special Stage in the first act of the Zone) and Sonic Heroes (if the player decides to enter the Bonus Challenge).