Pokémon HeartGold Version Easter eggs

Secret box wallpapers and Pokemon eggs
Head to the Violet City Pokemon Center and speak with the man (Hajime) standing next to the PC.

Using a phrase generator - there's a good one located here: <a href="http://www.filb.de/games/tools/aikotoba" target="_blank">http://www.filb.de/games/tools/aikotoba</a> - you can generate your own special grouping of words to tell Hajime. Depending on what you tell him, he'll offer you special PC box wallpapers, and Pokemon eggs!