Action Replay is the brand name of a series of cheating devices created by Datel, primarily used for changing the behavior of video games. Currently, Action Replay is available for a number of consoles including the Nintendo 64 and Nintendo GameCube which feature games in the Super Smash Bros. series; a version for the Wii has been released as well.
Nintendo 64 version
The version of Action Replay for the Nintendo 64 is inserted into the console's cartridge port. This version of Action Replay can be used to hack several features in Super Smash Bros.
Nintendo GameCube version
The version of Action Replay for the Nintendo GameCube attaches to the console's memory card slot, which, along with a separate disc, enables the player to access a debug menu, among other things. This version of Action Replay can be used to hack several features in Super Smash Bros. Melee, including the Debug mode, unlocking characters, infinite jumps, strange attacks variations, moveswapping (known for being very glitchy), and "super" codes which make attacks very fast. It can also be used to play with unplayable characters or on unplayable stages. The Gamecube debug menu has been used for TAS videos. For example: you can have Master Hand vs Crazy Hand vs Giga Bowser and also play in a 6 player match using the debug menu.
Action Replay Wii has an easier setup than the DS version. You can beat any game with the Action Replay. It also has a Max Media manager and a USB port on the SD card. Here's how to set it up:
Make sure your WII firmware is running v4.3
If it is not, update the system
Access Wii system settings 2
select the option Internet
select console information and take note of Wii Mac address
Now take your licence key, Mac address and the AR memory card