How do you battle with Jirachi on Pokemon Emerald?

YES

Hey. you know, you can get stuff like Kingdra and latios. ( Latios may be iffy ) Hey, I'm going to open a site to fix this soon but for now, stick with that answer, okay?

first, obtain Treeko, Mudkip, or Torchic from Professor Birch. After that you battle a wild Poocheana or (how ever you spell it). I think he's on level 3. Keep pressing A or B until the screen gives...

anything except the legendaries

You get it on Newmoon islandAnother answer: get the rare Pokemon coliseum bounes disk and trade over