You can get:
Heatran
Giratina (origin forme when holding the griessous orb)
Zapdos
Moltres
Articuno
Cressilia
Mesprit
Azelf
Uxie
Dialga
Palkia
regigiggas
Regiice/steel/rock if you have the special event regigiggas
you can see manaphy and add it to the pokedex by going to the Pokemon mansion and going to Mr. Blacklots room and talking to the book (this does NOT get you the Pokemon you only see it) but now you can look for it on the GTS
And rotom (i don't know if this is a legendary)
also you can get darkrai but you have to have members key
and arceus with the azure Flute
They are not found in the wild in Pokemon Platinum.
try to catch your legendary. It varies on which legendary depending on what starter you chose.
the 486 legendary is yo mama @#$%@
You cannot catch the legendary palkia on pokemon platinum but however you can use action replay to get it (most likely cheating)
ARCEUS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Noooooooooooooooooooooooooooooooooooooo!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Arceus (With Dragon plate)
Got the website in related links. It will tell you where to find the legendary pokemon, what levels they are and what they look like.
Empoleon is not a legendary Pokemon. It is the final evolution of Piplup, one of the starter Pokemon in Pokemon Diamond, Pearl, and Platinum.
no
it is not possible as legendary Pokemon are not breedable
you have to either catch a legendary or raise a Pokemon