Usually, you put in a code, and then that code will include a "trigger" to activate the code. For example, the code I used requires you to push L and Select to work. After you do, you go into the pokemart and a guy is there who gives you the Member's Card, which lets you go into an inn and fight Darkrai in a dream.. But that's exclusive to Diamond, Pearl, and Platinum. I'm sure there's a way to do it on HG and SS, like modifying a wild encounter, but.. people would know you cheated to get it, if you care about such things
na i wouldnt care as long as he is darkrai and doesnt look any different, im gud, by the way im very thankful for u helpin me out, but the thing iz if the action replay doesnt work then ima have to trade for it wit someone, do u think anyone wud give up darkrai?
Honestly I don't know. HG/SS are filled with legendaries. Really, there isn't much that's rare now given the Action Replay's popularity, and the Toys R Us/Gamestop events
*Spoiler below* They have Lugia, Ho-Oh, Latios, Latias, Zapdos, Atricuno, Moltres, Groundon Kyogre, Raquaza, Entei, Suicune, Raikou, and.. maybe more. There isn't much left to look for outside the game