To unlock these mini-games, do the following:
Snowkidz Snowboarding mini-game: Get 10 Specter Emblems
Specter Boxing mini-game: Get 20 Specter Emblems
Specter Boxing mini-game bonus characters: Successfully complete the Specter Boxing mini-game
Specter Boxing survival mode: Successfully complete the Specter Boxing mini-game
Jake Attacks mini-game: Get 30 Specter Emblems
Ape Ping-Pong mini-game: Get 40 Specter Emblems
Ape Ping-Pong mini-game bonus characters: Successfully complete the Ape Ping-Pong mini-game