The Game Boy game introduced two additional stats affecting the Tamagotchi's growth, Stress and Selfishness, additional games and food, daily competitions for the Tamagotchi to participate in, and the ability to praise the Tamagotchi for good behavior and make it use the toilet when it is getting ready to poop. The praise and toilet features would later be implemented to other versions of the physical Tamagotchi toys. The game also introduced the Tamagotchi researcher Professor Banzo and his assistant Mikachu, who help run the Tamagotchi laboratory and give the player advice.
A sequel, Game de Hakken!! Tamagotchi 2, was released for the Game Boy in Japan four months after the original, featuring new Tamagotchi characters based off insects and marine animals. The player controls Mikachu as she explores the overworld in search of Tamagotchi eggs and items while working for Professor Banzo. The new Tamagotchi species would get their own toy releases in the Tamagotchi Ocean and Mori de Hakken!! Tamagotchi devices. Game de Hakken!! Tamagotchi 2 was never released outside Japan.
Another sequel, Game de Hakken!! Tamagotchi Osutchi to Mesutchi, was released for the Game Boy Color in Japan in 1998. This game was based on the Tamagotchi Osutchi and Mesutchi toys, which were the first Tamagotchi devices to allow players to connect their toys together to have Tamagotchis marry and produce babies. This game was also never released outside Japan.
Tamagotchi and its sequels feature examples of:
- Bowdlerise: The cross-shaped tombstone seen on the death screen when a Tamagotchi dies is removed in the North American release of the first game.
- Bug Catching: Mikachu and Professor Banzo are shown dressed up for bug catching and carrying bug nets on the cover of Game de Hakken!! Tamagotchi 2 as well as in the main menu. In the main menu, Banzo is also wearing the stereotypical straw hat, tank top, shorts, and sandals.
- Character Name Limits: Each Tamagotchi's name is restricted to four characters in the Japanese version and five characters in the North American version.
- Continuity Cameo: In the second game, a plush of Mimitchi can be seen in Mikachu's room.
- Cultural Translation: In the first game, the rice ball food item was changed to a piece of bread for the North American release.
- In-Universe Game Clock: Each hour of in-game time is equivalent to about three minutes of real time, causing time to go faster than in the toys (which run in real time) to make up for the fact that the Game Boy can't be left on at all times. 24 hours is still equivalent to one "year" in a Tamagotchi's life cycle, the same as in the toys.
- Luck-Based Mission: In the sequel, one of the games you can play with your Tamagotchi is a guessing game where you uncover tiles, similar to a scratchcard. Whether you win or lose is based on if you randomly uncover hearts or skull tiles.
- Random Encounter: In the sequel, a boulder will sometimes appear at random in the Tamagotchi tanks and threaten the player's Tamagotchi. If the player doesn't dodge the boulder on time by pressing B, it can fall on the Tamagotchi and injure or even kill it. A similar feature was incorporated on the Tamagotchi Ocean and Mori de Hakken!! Tamagotchi toys.
- Sound Test: In Game de Hakken!! Tamagotchi 2, the player can access a sound check menu to listen to background music and sound effects by interacting with the boombox in Mikachu's room in overworld mode.
- Three Quarters View: The overworld mode in Game de Hakken!! Tamagotchi 2 is portrayed in a three-quarters perspective from above.