No, kecleon appears in the grass normally like any other wild pokemon. But you have to use the Pokeradar, and it's kind of rare. It appears on Route 210 (North).
first you go to route 210 use defog then you use poke radar in any part of the grass and to catch bagon you use a quick ball or a timer ball and if its night time use a dusk ball.
in diamond and pearl first you go to veilstone city.then go to spring path.use rock climb.and then you see the cave,go inside and then you have to use defog and rock smash
You don't necessarily need Defog, but if you want to use it, you use it 2 or 3 times.
you have to go to pokemon team and then select the pokemon which knows defgog and then you see the word defog select that and then go to the place where you wantto defog and then the fog will go.
Feebas is ultra rare but if you have the time you can catch him. He is in a pond in mount coronet from the Celestic town entrance. Use defog then use the good rod on the water. It WILL take a while but its worth it when he evolves.
The way to catch a Duskskull in Diamond or Pearl is to get the National Pokedex and then head off back to victory road. One should have a Pokemon that can use defog. You should go into Victory Road from the top side or the entrance from the Pokemon League. There is a series of paths that can get you there and the entrance is in the top right. For short, you catch it in route 224 in the grass.
Go to Route 210 and use the Pokeradar, he's fairly rare but you'll eventually find him.
to get rid or fog or mist who is stopping your sight of playing
use the hm-Defog (found in the great marsh-the "ace trainer" person has it)
You can't catch mewtwo in Pokemon diamond. It's better if you use Action replay code.
how can i catch arceus
You can't catch it in Diamond, only in Pearl. But hey, you can catch Larvitar in Diamond but not in Pearl. It evolves into Tyranitar which is stronger. It's in Route 207 and you need to use Poke Radar.