Game Guy appears similar to a regular Shy Guy, with the exception of the blue bow tie on his neck. Also, Game Guy has the ability to fly and is demonstrated to be athletic, given how he does backflips.
Game Guy appears on every single board in Mario Party 3 on the Game Guy Space. Whenever one lands on a Game Guy Space, Game Guy swoops down and swipes all of the victim's coins. He then forces them to play a Game Guy minigame. Game Guy also appears during the end credits doing his backflip pose. After the player has completed Story Mode with at least 8 S rankings (thus becoming a Miracle Star), Game Guy's room is opened. This room is where one can play his minigames until he/she reaches one thousand coins. This causes the minigame Mario's Puzzle Party Pro to be unlocked.
Mini-games that Game Guy Hosts
Game Guy hosts the following minigames;
- Game Guy's Magic Boxes: In this mini-game, there are two boxes; one which contains Toad and one which contains Baby Bowser. If the player picks Toad, he/she has the choice to either stop playing or continue. If the player picks Baby Bowser, he/she loses the mini-game. This mini-game is one of the most common mini-games that is hosted by Game Guy.
- Game Guy's Lucky 7: In this mini-game, Game Guy and the player need to roll dice blocks to see who gets the highest number without falling off. The highest number one can roll is a six. The player may win if he/she is on a higher step than Game Guy if Game Guy falls off, or if the player is on the same space as Game Guy. However, if one lands on the seven, his/her coins becomes increased tenfold.
- Game Guy's Sweet Surprise: In this mini-game, a big and small Chain Chomp can be seen eating cake. The one that finishes it first is the winner. The player must choose which Chain Chomp is the winner. Though the big one is known to win, the smaller Chain Chomp has the possibility to win as well. The big Chain Chomp doubles the player's coins and the smaller Chain Chomp varies from four to thirty-two times if the correct one is picked.
- Game Guy's Roulette: In this mini-game, Game Guy spins a shell around a roulette wheel; whatever it lands on decides on how much of the player's coins being multiplied. Koopa's space is the largest at only double coins and Game Guy's space is the shortest being at 64 times. This mini-game is the most rare and considerably the hardest mini-game hosted by Game Guy.
- Game Guy is one of the few Shy Guys species that doesn't try to harm the player. The other Shy Guy species is Gourmet Guy who appears in Paper Mario.