Pokemon number 150 is Palkia, you can get it on the pokedex by trading, battle a friend or seeing the old lady in the library who shows you a picture of Palkia which is then added to your pokedex.
in the grate marsh
you have to see 150 Pokemon then talk to professor oak..
150
there are exactly 493 pokemon, i know!
You need to obtain data (see not capture) on all 150 Sinnoh Pokémon. I would recomend that you battle all possible trainers in the game to get your pokédex up also to see Dialga you must trade it from diamond.
you cant find it, you have to see all the Pokemon sapphire.
for diamond and pearl there are 150 Pokemon u need to see . in plat nium u neeed to see 210 Pokemon.
First you have to find all 150 Pokemon then talk to professer rown and then you p. oak comes and opens it. And you then get the national pokedex.
Pokemon Number 149 (Dialga) Cannot be found in Pokemon Pearl, he is only available in Pokemon Diamond, where as Number 150 (Paulkia) cannot be found in Pokemon Diamond. If you need to fill the spot to complete the PokeDex, you can see #149 from a lady in Celestic Town.
Pokemon 150 is Palkia, the Space Pokemon. You can find it at Spear Pillar.
See all 150 Sinnoh Pokemon
Palkia is the last Pokemon in pearl and in diamond you find him in a book that an old lady shows you and in pearl you find at spear pillar on mount coronet. (I really hope this helps you on your wild adventure)