Catching ‘em all has generally been the premise of the Pokémon franchise since it debuted in the mid-1990s, and that task first became a little more difficult when the second generation of games debuted 20 years ago. Pokémon Gold and Pokémon Silver first arrived on November 21, 1999 in Japan before making their way to the rest of the world the following year.

These Game Boy Color titles opened up a whole new world to explore for Pokémon fans. The games introduced players to a new region, Johto, with 100 new monsters and eight new badges to collect. A new storyline introduced players to the region and these new Gym Leaders, but also continued certain things that started in Red and Blue version, such as the issues with the villainous Team Rocket. Those who finished the Johto challenge were then able to revisit Kanto, seeing how things have changed in the three years between the stories of Red/Blue and Gold/Silver.

Pokémon Gold and Silver continued the massive success of their predecessors and helped the Pokémon franchise go from a multi-million dollar franchise into a multi-billion dollar one. By 2010, more than 23 million copies of Gold and Silver had been sold. The second generation of games was also critically acclaimed, with the variety of improvements made, such as the day/night system that ran off an in-game clock, particularly praised.

Despite several more generations of Pokémon games having released over the last two decades (including this week’s release of Sword and Shield on the Nintendo Switch), Gold and Silver remain fan favorites – they also remain the only games in the franchise to allow players to travel between regions, a feature that many fans continue to ask for again. These games would be remade several years later for the Nintendo DS as Pokémon HeartGold and SoulSilver, which themselves went on to become some of the best-selling DS games of all time.