Use:
The first WiFi Event in Pokémon Heart Gold & Soul Silver is attributed to the PokéWalker peripheral. When you receive this gift, you will discover that you have obtained a new PokéWalker course. This PokéWalker course is filled with Pikachu. However, there are Pikachu here whom have a special attack that Pikachu cannot normally learn.

Use:
The second WiFi Event in Pokémon Heart Gold & Soul Silver gives you a special Mew. This Mew is Level 5 but knows no special moves. However, it is the first Pokémon that has the Premier Ribbon attached.

ミュウ Level 5	OT: ススム	Trainer Memo: ??? Nature. Date of Obtaining Wi-Fi Event. Apparently had a fateful encounter at Lv. 5	Attacks: Pound	Ribbons: Premier Ribbon
	ID No: 11219
	Hold Item: None

Use:
The third WiFi Event in Pokémon Heart Gold & Soul Silver gives you the key item; Enigma Crystal. When you take this item to the Pewter City Museum and take it to the guy who revives your fossils, he will discover that it is the Soul Dew. Soon after, Steven Stone will arrive and will tell you it is an incarnation of the souls of Latios & Latias. Once you leave, Latios or Latias will arrive and challenge you depending on the version you have.

SoulSilver	HeartGold
Level 40	Level 40