Sean Special

 La version 5200 tiene un easter egg para poder jugar 4 jugadores.

Pero no se preocupen porque ya existe la version modificada para tal caso: https://manillismo.blogspot.com/2013/12/tennis-m4.html

• A prototype exists, dated 11-19-82, that shows the name as The Atari Open on the title screen (picture #1). There’s no player name entry, so there’s nothing next to the scores (picture #2). It also doesn’t have the secret 4-player mode described below.

• Animator Dave Joly felt the game might have been called Vic Braden’s Atari Tennis or Vic Braden’s Tennis at some point during its development.

• Secret 4-player mode! At the first game screen, press 0 on the keypad to put the game in doubles mode, and then press 4 for “Sean Special” mode (for programmer Sean W. Hennessy – picture #3). {John Hardie}

• This is the same as Atari Tennis for the 400/800, except Atari Tennis has a title/trophy screen (picture #4), and a copyright date of 1983 (instead of 1982), but it lacks the 5200 version’s hidden 4-player mode (although the text for the message is still in the code).

• The “RealSports” moniker was added to the packaging after the game was completed, which is why it’s not mentioned anywhere onscreen.

http://www.ataricompendium.com/game_library/easter_eggs/5200/52rstennis.html