What if I told you I would trade a Manaphy for a Jirachi?

Event Pokemon aren't needed to complete it...

manaphy isnt considered an event pokemon because it was available from the original pokemon ranger game

yes it is, otherwise my national dex would be considered complete by the boy in the professors lab

In Pokémon Diamond and Pearl, once the player has at the very least seen 150 Pokémon of the Sinnoh Pokédex, (Manaphy is the only Pokémon in the Sinnoh Pokédex in these games that doesn't need to be seen), and talks to Professor Rowan, Professor Oak will arrive to upgrade the Pokédex to include the National Order. This, however, is not required to be able to receive Pokémon not in the Sinnoh Pokédex list via trades with other Generation IV games. In Pokémon Platinum, the requirement is the same, however, all 210 Pokémon in the expanded listing must be seen, including Manaphy. However, Manaphy can now be seen without trading by reading the book at the Pokémon Mansion.
In Pokémon HeartGold and SoulSilver, Professor Oak gives the player the National Pokédex before he/she boards the S.S. Aqua for the first time. However, as with Diamond, Pearl, and Platinum, it is not required to obtain Pokémon not in the games' regional Pokédex (in this case, the Johto Pokédex). The Pokémon Mew, Celebi, Deoxys, Jirachi, Manaphy, Phione, Arceus, Shaymin, and Darkrai are not needed to complete the National Pokédex.
In Pokémon Black and White, Professor Cedric Juniper upgrades the player's Pokédex to the National mode when the player first leaves his/her own house after defeating N and Ghetsis. As with previous generations, event Pokémon including Keldeo, Meloetta and Genesect are not needed to complete the National Pokédex. In Black 2 and White 2 Cedric Juniper will upgrade the Pokédex in player's house, after (s)he defeats the Champion.

I have 637 caught, and Im not getting the reward for the national dex.

The reward IS just a certificate.

thats not important to me, it means manaphy and phione are for some reason necessary

Well, they're not.

oh shit youre right, i forgot to evolve dusclops into dusknoir. i was mistaking the 637th for my darkrai.

I saw this and I was like....I have a Manaphy... ._.

well im fresh out of legit shinies so i wouldnt have anything to trade anyway

I also have a Dusknoir if needed.

would you prefer a level 65 growlithe, or a level 1 with close combat egg move? i also have a few extra outrage horsea

outrage horsea :D

Yeah it's my prize pokemon but I wouldn't mind trading it. I don't play platinum much anyway but I've gotten to far in it pokedex wise and Battle Frontier to restart.