Any Pokemon Platinum Strategy guide should always include the various ways to catch Regigigas. Catching it can become confusing if you don’t know how to make it appear, and it can be a lot of work if you don’t have direct access to the Pokemon needed.
Every game in the pokemon series has introduced its own legendary pokemon. Pokemon Platinum also sees a return of some legendary pokemon from previous games. Finding all the pokemon on Platinum means finding all the legendaries too, which takes a little bit of effort, some luck and patience.