Dobutsu no Mori+
December 14, 2001
In Dobutsu no Mori+ the complete Famicom/NES game Ice Climber is featured as a playable mini-game, though it's normally unaccessable and was only given to players that used a service to transfer data from the Nintendo 64 version of Dobutsu no Mori to Dobotsu no Mori+ on GameCube.
It returns in international versions of Animal Crossing, where it was made available by scanning the respective e-reader card, released in the fourth series of Animal Crossing-e cards.
See here for other NES games included in the game.
Copyrights for both series are held by Nintendo.