One of the easier ways to fill up the Pokedex in any of the main Pokemon games was by breeding Pokemon and hatching eggs. As expected, this mechanic makes a return in Brilliant Diamond and Shining Pearl. This requires trainers to bring one female and one male of a compatible Pokemon species to the Pokemon Daycare. For those looking to hatch Pokemon available via breeding, they may need the help of Ditto.
Since Generation 2, players have stuck Ditto in the Daycare with a Pokemon of the species they want to breed. It's only natural that trainers would want to know where they can catch Ditto in Brilliant Diamond and Shining Pearl too. However, there are some requirements that need meeting before players can find Ditto in the wild.
Complete the Sinnoh Dex
Players aren't going to be able to catch Ditto until they've received the National Dex. To get the National Dex, trainers need to see every Pokemon in Brilliant Diamond & Shining Pearl. This doesn't mean catching them all. Simply battling or looking at pictures in-game will register a Pokemon to the Pokedex.
As for version-exclusive Pokemon, speak to Cynthia's grandmother in Celestic Town to register them. In Brilliant Diamond, she will show the trainer Palkia. In Shining Pearl, players will see a picture of Dialga instead. For those worried about Exclusive Pokemon in the wild (such as Stunky and Glameow), these can be seen by battling NPCs during the course of the game. In fact, many of the grunts/commanders of Team Galactic will have Pokemon not available to catch in the wild in both Brilliant Diamond and Shining Pearl.
With this complete, return to Professor Rowan in Sandgem to receive the National Dex and the PokeRadar. The National Dex will allow trainers to register up to all of Brilliant Diamond and Shining Pearl's 500 Pokemon, meaning never-before-seen Pokemon will now become available in the wild. This of course includes Ditto.
Catching Ditto
Players have a chance of finding Ditto in two areas of the Grand Underground: Dazzling Cave, and Stargleam Cavern --but only after the Elite Four is defeated. It can also be found on Route 218 via the PokeRadar. Note that the PokeRadar can only be used in short grass.
With the PokeRadar in hand, step into the grass on Route 218 and look for shaking grass. Bring Repels to ward off other wild Pokemon. Ditto is fairly common in the area, so when finding one, toss a Quick Ball to capture it. Luckily, Ditto doesn't copy the catch rate of Pokemon, so it should be fairly easy to catch if the Quick Ball strategy fails.
If players have a bit more patience, they can use the PokeRadar to Shiny Hunt for Ditto. However, know that breeding a Shiny Ditto doesn't necessarily make its offspring a Shiny.
Pokemon Brilliant Diamond and Shining Pearl are available now on Nintendo Switch.
