Hi there. No, you cannot "catch" a Ho-oh in Pokemon Diamond and Pearl, however, there are other ways that you can get a Ho-oh into your Diamond and Pearl version of Pokemon:
1) You can complete the tasks necessary in order to unlock Ho-oh in Pokemon Colosseum and then transfer it over to your Ruby/Sapphire/Emerald version of Pokemon, and then migrate the Ho-oh into your Pokemon Diamond and Pearl versions of the game.
2) You can get one over the GTS if you've already seen a Ho-oh in your game.
3) You can use an Action Replay to hack one into your Diamond or Pearl version of Pokemon, or you can hack one into your Ruby/Sapphire/Emerald version of Pokemon and migrate it into your Diamond and Pearl versions.
4) You can trade for one from one of your friends.
Hope this helps :)
The Jolly Green Giant, yo hoho!
Ash has seen it three times but never actually met it.
ben? yeas. yeas. nu. nu. nu. hoho hoho hoho hoho hoho hoho augh augh yeas ben? nu.
You can catch Hoho at night.
magic
Agreeing to meet in at a certain place and time.
by some of his tickets and go
in heart gold go to top of bell tower you meet hoho in soul silver go to whirl insland get lugia
hoho
no
flying fire
hoho