A modder has hand-coded a replay feature for Super Smash Bros. Melee, and it will work with the game — playing either on GameCube or Wii — simply through a memory card. No additional modding, homebrewing or other advanced methods necessary.
The replay feature is part of Dan Salvato's 20XX Tournament Edition for Super Smash Bros. Melee, which he will release in November for free. It's not like a replay camera common to many sports video games. The replay not only records the entire match, it allows a player to re-enter the match and take control of it at any point. As Salvato points out, this is of great benefit for practice and training.
Super Smash Bros. Melee launched in 2001 for the GameCube but remains a significant event at fighting game tournaments, including most recently EVO 2015.
The mod also incorporates the standard features of a replay, including fast-forward, rewind, frame-by-frame advancing, pause and the like. There's also a cool toggle that shows each character's hit boxes. Salvato is introducing some other features with the 20XX Tournament Edition, more of which can be seen here, but the replay functionality will no doubt get the most people interested.
The mod will be "100 percent free to download and share" when it arrives, though Salvato is offering "pre-orders" for the cost of a memory card and shipping it. The mod is for NTSC copies of Super Smash Bros. Melee. More info is here.