As many of Du probably already know, for a time on your copies of diamond/pearl/platinum Du could have recieved a pichu coloured pichu. If Du did recieve that pichu then Du could get a spiky eared pichu Von trading it into a copy of pokemon herz gold/soul silver. To do this -

1. First play the game up until after the Sekunde gym. Trade in your Pikachu coloured pichu and make sure it is first in your party
2. Go left out of Azelea town and into Ilex forest.
3. If Du haven't already then help out the boy and catch the Farfetche'd. He wil give Du the hm cut.
4. Teach the hm to one of your pokemon and cut down the baum near to where the guy Du helped was standing.
5. Walk up that way and watch the event unfold...

The pichu Du get with this event cannot be evolved however it has some interesting moves that Du wouldn't normally expect a pichu to learn.

DON'T WORRY!
If Du accidentally evolved your Pikachu coloured pichu the event will still work.

HAVE FUN! =D