Authentic EA Sports 4 Way Play Adapter SEGA Genesis Multiplayer New NIB Sealed found in our warehouse that we purchased direct from Electronic Arts over 25 years ago! Please note that these do not have shrinkwrap and this is how we purchased them from EA. 

 4 Way Play is an accessory created by Electronic Arts for the Sega Mega Drive. It allows for up to four players to play together in certain games. Largely, mostly games designed by EA itself supported it. When first released, Sega's official Team Player multi-player adaptor was not compatible with 4 Way Play games. Later releases fixed this incompatibility issue.

The device itself plugs directly into the system and has no wires sticking out and attaches to the front of the system like an extension. To attach like this it plugs into both controller ports. Due to the way it is plugged into the system it is incompatible with devices such as the Sega Multi-Mega and X'eye.

Compatibility
Genesis Cartridge
Australian Rugby League
Bill Walsh College Football
Bill Walsh College Football '95
Coach K College Basketball
College Football USA 96
College Football USA 97
Elitserien 95
Elitserien 96
FIFA 97: Gold Edition
FIFA International Soccer
FIFA Road to World Cup 98 (Mega Drive)
FIFA Soccer 95
FIFA Soccer 96
Gauntlet IV
General Chaos
IMG International Tour Tennis
MLBPA Baseball
Madden NFL '94
Madden NFL '95
Madden NFL 96
Madden NFL 97
Madden NFL 98
Mega Bomberman
Mutant League Hockey
NBA Live 95
NBA Live 96
NBA Live 97 (Mega Drive)
NBA Showdown '94
NHL 95
NHL 96
NHL 97 (Mega Drive)
NHL 98 (Mega Drive)
NHL Hockey '94
PGA European Tour
PGA Tour 96
PGA Tour Golf III
Pelé II: World Tournament Soccer
Rugby World Cup 1995
Street Racer
Triple Play 96
Triple Play: Gold Edition
Wayne Gretzky and the NHLPA All-Stars
Mega-CD
Bill Walsh College Football
Bouncers
FIFA International Soccer: Championship Edition
Mighty Mighty Missile!
NHL Hockey '94