The Spiky-eared Pichu

Like Pokémon Platinum, Heart Gold & Soul Silver have got special details implemented within the game if you send certain Pokémon over.. In Platinum, this allowed for new forms and capturing of certain Pokémon. However, Heart Gold & Soul Silver have got a slightly different take on this.

If you send over the special Pikachu Coloured Pichu obtained from an event or over WiFi, a special feature will activate. This event takes place in Ilex Forest. When you go by Celebi's Shrine in Ilex Forest when you have the Pikachu Coloured Pichu in your party, a Spiky-Ear Pichu will appear. If you inadvertantly evolve the Pichu into a Pikachu or eventually a Raichu, the event will still work

With the Pikachu Coloured Pichu and the Spiky Eared Pichu in Ilex Forest, the Spiky Eared Pichu shall then join your team. This Pichu is completely unique and you will be unable to get it by any other means. However, there are a variety of new details about it.

The Spiky Eared Pichu is always female and appears to be given to you at level 30. It has many attacks that Pichu would not normally know. The details are as follows

Pichu
Spiky-eared Pichu
Level 30
OT: Yours Trainer Memo:
Naughty Nature.
Date of Obtaining
Caught at Ilex Forest. Met at Lv. 30
Attacks:
Helping Hand
Volt Tackle
Swagger
Pain Split
ID No: Yours
Hold Item:
Zap Plate

However, there is a draw back to the Spiky-eared Pichu. First, the Pichu is unable to evolve into Pikachu and as such not into Raichu. In addition to this, it is unable to be traded to other games.

Professor Elm's Research

If you take the Spiky Eared Pichu to Professor Elm's and have it at the front of your party, you will get some backstory of the Pichu. Professor Elm will say that Professor Oak has recently discussed Celebi's time travel abilities and that the Pichu proves his theory. The Spiky-Ear Pichu arrived in this time by Ilex Forest through time travelling with Celebi, which explains why it cannot be traded and why the trainer needs to take care of it.

In addition to that, all the time travelling it has done has also caused its body to stick in its current state. Professor Elm then goes to contact all the Pokémon Centre attendants to prevent the Spiky Eared Pichu from being used in game to game trades