Just in case you missed it:
Pokemon White Wild Modifier (L+R) (Select)
Press L+R, you will get 649 Master Ball and 100 Ultra Ball, Toss to change amounts to Pokemon number and level respectively. Master Ball Quantity = NationalDex Number. Ultra Ball = Level. Press Select before heading into grass.
Code:
94000130 FCFF0000
02233FCC 02890001
02233FD0 00640002
D2000000 00000000
94000130 FFFB0000
DA000000 02233FCE
D3000000 00000000
D7000000 02250030
D3000000 00000000
DA000000 02233FD2
D3000000 00000000
D7000000 02250032
D3000000 00000000
D9000000 02250030
D3000000 00000000
C0000000 0000002F
D6000000 02250030
D2000000 00000000
Of course, if you're using Pokemon Black, you should use the one Darkrai got. But if you're having trouble with his, I assume you're either using Pokemon White or your Action Replay's firmware hasn't been updated yet... I had the freezing issue before because I was using Pokemon Black codes when I was playing Pokemon White. When I found the above codes, it worked
BTW I'm using Original Nintendo DS so you might have to do one thing extra to get these codes working... I will need help from other members here to determine this, though.