Where do you catch Pichu on Pokemon Pearl?

You can't catch Pichu in Pokemon Pearl directly. Pichu evolves from Pikachu, which is a wild encounter in Pokemon Pearl. However, there are a couple of ways to get a Pichu:

1. Breed a Pikachu: If you find a Pikachu and breed it with another Electric-type Pokemon, there's a chance it will produce an egg that hatches into a Pichu.

2. Trade: You could trade with someone who has a Pichu for another Pokemon in your collection.

Remember, breeding and trading are ways to get Pichu in Pokemon Pearl, but you won't encounter Pichu in the wild.