There are lots of different ways to catch some of these more difficult to get Pokemons below. We've just outlined some of the possiblities...
To catch Castform go to the Trophy Garden of the Pokemon Mansion.
To catch Darkrai go to the abandoned Inn in Canalave City. To enter the inn you will need a membership card which can either be obtained with Mystery Gift or at a Nintendo event.
To catch Gible go to Oreburgh City and use Cut to go underneath Cycling Road and he'll be inside Waywards Cave.
These Pokemon can be found underneath Cycling Road or outside Stark Mountain if you have Pokemon Emerald in the GBA slot.
To catch Heracross buy honey from a man selling it for $100 in Floarama Town and spread it on the golden trees you see during the game. If the tree starts shaking there is a Pokemon inside and there is a 10% chance it will be a Heracross.
To catch a Munchlax give a Snorlax a Full Incense and put it in the Daycare. When you get an egg run around for 10,240 steps and it will hatch into a Munchlax. There is also a chance of catching Munchlax by spreading honey on certain trees. It will become obvious which ones that you can spread honey on once the honey becomes available to you... The trees like slightly different and goldeny color.
You must migrate Regice, Registeel and Regirock into the Palpark and catch them. Then go to Snow Point City and directly north of the gym to a temple and he'll be on the bottom floor.
Speak to the man in the cave on Iron Island and he'll give you an egg. Run around for 6,000 plus steps and a Level 1 Riolu will hatch.
To catch Rotom you must first have the National Dex. When you have this go to the Eterna Forest and look for the old chateau. Find the room with the TV and press A on it. The TV will ask you to take a closer look and if you press 'Yes'
You will battle a genderless Level 15 Rotom which can breed with Ditto.
Catch a Level 35 or 36 Wobbuffet in Lake Valor and surf to the bottom right corner of the lake to where there is grass and use your Pokerader. Cresselia will not be able to escape because Wobbuffet has the ability Shadow Tag.
To catch Dratini go to the Waterfall area of Mt. Coronet and fish using the Super Rod. You can also get a Dratini if you migrate them from previous versions using Pal Park.
To catch Dialga go to the south side of Mt. Coronet by Route 208 and use a move like Flame Thrower or Mach Punch and throw Ultra Balls.
To catch Feebas enter Mount Coronet at the entrance near Eterna city. You must have a Pokemon with strength and Rock Smash and have the super rod.
When you have beat the game go back to Bebe in Hearthome city and if you have an empty slot and the National Pokedex she will give you an Eevee.
When you have defeated Team Galactic at the Valley of Windworks go back on a Friday (must be Friday) and you will see Drifloon.
To catch Giratina you need to have the National Pokedex, Surf, Rocksmash and Rockclimb. Go to Veilstone City and go down the east border on route 214 until you reach a path called 'Spring Patch'. Follow the path to 'Sendoff Spring' and look for Turnback Cave and you'll find Giratina inside.
To catch Heatran complete the National Pokedex and go to Stark Mountain and talk to Bucky (man with red hair). He joins you and then leaves to return the Lava Rock he took from the cave. When you now go to the cave you will find Heatran in an empty room there.
To catch Lavitar go to Oreburgh City and keep going up the stairs until you reach a large patch of grass on route 207. Use the Poke-Radar to locate it as this Pokemon is rare.
To get Azurills give a female Marill or Azumarill a Wave Incense to hold and then breed it with a male Marill. If you try this without Wave Incense the egg will be a Mariil.
When you have got the National Pokedex go to route 218 by Canalve City and use the Pokemon radar.
Track Mespirit with the Poketch and then use the move Mean Look and put it to sleep.
When you have Dialga or Palkia go to Lake Acuity and use False Swipe and Dusk Balls.
Catch Manaphy and breed it with a Ditto to make a Phione.
Added by: Sanzano Oct 19th 2007, ID#5189