How do you get more than one Rotom in Pokemon platinum?

In Pokémon Platinum, you can obtain multiple Rotom by trading. Here's a step-by-step guide on how to do it:

1. Catch the First Rotom:
   • Location: Old Chateau in Eterna Forest.
   • Requirements: You need the National Pokédex to change its form, but you can catch it with just the regular Pokédex.
   • Time: Nighttime (8 PM to 4 AM).
   • *How to Catch:*
     • Go to the Old Chateau.
     • Enter the room with the TV.
     • Interact with the TV to encounter Rotom.
     • Capture Rotom.
2. *Trade for Additional Rotoms:*
   • Since you can only catch one Rotom per game, you'll need to trade with other players to obtain more.
   • Use another Nintendo DS and a copy of Pokémon Diamond, Pearl, or another Platinum game.
   • Catch a Rotom in the other game(s) by following the same steps.
   • Trade the extra Rotoms to your main Platinum game using the Union Room or Wi-Fi Club.

By repeating this process, you can accumulate multiple Rotoms in Pokémon Platinum.