Pokemon games are famous for having mysterious elements added to the game, be it the Missingno Pokemon in Red and Blue, or the Ilex Shrine in the Pokemon Gold and Silver games; however, as it turns out the latter wasn’t actually intended at all. Players who visit the Ilex Shrine location in Gold and Silver assume that something is going to happen because of a rumor that started in online message boards. The rumor has it that the mythical Celebi could be summoned at the shrine’s location by bringing a specific item and interacting with the shrine.
In a recent interview with Siliconera, Hironobu Yoshida Celebi’s designer stated that the development team was confused when they heard rumors about catching Celebi in Gold and Silver because nobody remembered adding Celebi to the game. "The leading rumor in Japan was that you needed to bring both the Rainbow Wing and Silver Wing to the shrine, which would make Celebi appear," said Yoshida. He also recalled that "back then they would use additional sprite parts to give texture to rooftops, staircases, rocks, and more, they might have added in the shrine with these additional sprites just to spruce up the area. Basically, it was probably just part of the background. [and nothing special]"
Of course, Celebi is the Guardian of the Ilex Forest, so it's only fair to assume that it will appear at some location in the Forest, but that never happened. Even though Celebi's Pokemon data was found in the game files, but this legendary Pokemon was not catchable in the Gold/Silver version of the game. Celebi became catchable in the Pokemon Crystal version of the game where players had to unlock the in-game quest to catch it. However, Pokemon SoulSilver/HeartGold did away with all the mysteries and made Celebi a downloadable Pokemon through GameStop.
Fans still assume that the Ilex Shrine had some special purpose, but it’s only part of the background as stated by Yoshida. Also, Takao Unno, the art director behind the game said, "Nobody on the original staff remembers what the shrine is for, and that's the true mystery behind Celebi." Pokemon Gold and Silver were released in 1999, and rumors like this have been circulating all over the web for 20 years now, it's good to finally get closure on one of the biggest mysteries of Gold/Silver. However, not all fan theories were shot down, some Pokemon Gold/Silver fan theories were actually confirmed by developers either directly or by later additions to the franchise.
Pokemon Gold and Silver is out now for Game Boy and Game Boy Color.