i found this on gamespot
| UNLOCKING ONAGA AS PLAYABLE | MKDO501 |
--------------------------------------------------------------------------
Currently Onaga is unavailable to be playable outside of a cheat device
such as Codebreaker or Gameshark2. As of this writing there are no kodes
for Action Replay MAX to control him, and I am unsure of GameShark2. I
used the Codebreaker kodes to play as Onaga. These only work with the
normal version of MK:D, not the Premium Package. Here they are:
Master Kode (Must Be On)
------------------------
B4336FA9 4DFEFB79
352BA795 CF074F86
6F456B84 D6D359A2
E3956DBB 6FABD13F
Player 1 is Always Onaga
------------------------
0C5CCBD7 97917575
Player 2 is Always Onaga
------------------------
B485EAF4 B477ED42
Note: These codes will enable Onaga for both Arcade and Puzzle modes.
If a technique to official unlock Onaga without a cheat device, this
guide will be updated with that information immediately.

some how I dont like the ideal of playing the bosses. I mean they are cheap. And it adds some thing to a boss if you cant play the boss. I was upset with MKT when you can play Kintaro, Goro, Khan ete. I mean it takes something away from the boss.

U wouldnt happen to know the kodes on how to play as Kitana, Cage, Kung Lao, Young Shujinko, and Monster. I know i seen a while back, but cant seem to find the kodes. If u could find em that would be awesome.

If you are talking about the ones for AR Max.....
Character Modifier/Replace Scorpion into:
HZ3T-3QDV-560PJ
Baraka
JVQN-QJ4Z-BM6AR
39QB-W5D5-G231V
K27X-JRDQ-Q0VC3
MA87-3WWV-ERMFG
EFPD-RETD-BXUQH
Noob
D28A-19KJ-1VRVF
6D8E-T7QC-RZP7A
RG7C-HF4N-CYPEC
5Y5P-6BJE-Y912P
2HTR-U0XZ-CRNJN
Sub-Zero
RUFM-KTMR-084T5
KR85-ZBAG-ENVF8
P3V0-KKR5-YZMN2
01EY-C691-95GCX
BKVW-0HZN-RPKXU
Mileena
DRG1-KYR0-JRVCM
TH0B-AAKA-29PME
34BJ-99VZ-N07ZY
3RQC-DH09-9JHMZ
1W4G-E03D-P8VU4
NightWolf
FFDF-895N-NN00T
CBD0-B4RH-PREG2
YGYZ-0ND3-JNH6W
MCDK-8JHR-PBDX0
9FK0-X9K4-TP4EW
Ermac
H0G8-HKZ4-CPGGR
95BU-7NM3-N3K2W
CGT3-8WBE-6Y5RX
TZKT-UNN6-49QFM
N69M-2D02-60B8V
Ashrah
JFNM-6VDP-VT371
CXZG-N93Y-Z2BWB
8ZTR-3RVZ-Z4NK5
7QAG-QYQD-H6DCA
AH5X-RWAK-FD8UP
Sindel
ND8K-P6QM-H5KH6
CZH2-9UEG-61F72
PPEJ-KUW6-CPXZ5
9VE6-NEB9-QHE76
4M2X-VBFH-X65CD
LiMei
6T1M-V5F8-45JPZ
NU0J-4Z9B-EM8HD
M30U-W31N-ZR4RQ
2EMC-14B0-JDJEW
B2JZ-H75J-4QK3Y
BoRaiCho
VV2R-KCNW-G9BA6
E9PH-6EYP-W2EFP
8TMU-ZJCX-QYE2M
JT24-HRUC-GA7PG
QVZ0-HZA0-C45Z5
Hotaru
WTXA-J60F-XNJQ8
UVVZ-PR2T-JCWJ3
WY5Y-B01E-GRUD8
RMHJ-ACWK-0K7XM
86U7-E00B-HPG1R
Kenshi
X2Y6-QVBR-RY8JB
1N9E-HDFH-60GDA
FPDF-1H8U-W85BM
KCZT-EFRR-QCX7W
8XMX-ZFR0-Y5F6V
Smoke
5EKR-5HXA-5Y9W4
NKQN-AYCY-084TX
33BQ-GBUQ-6JYC6
35UB-HK1P-4HWT6
NCGK-FT2P-94R0W
Havik
9U9B-M2DJ-RP7CX
CTAC-4FD4-JG733
24FP-K613-WB83F
ZHXH-82JU-YYGGJ
T3MN-B5WZ-UEQ9W
Tanya
ZUJJ-PB8B-DU52W
876D-GW00-53XV4
JA0J-TNY8-660GA
UTKV-9DFH-YGBR6
ZU60-G2M6-RUHDF
LiuKang
2RW0-ZEUX-40PEH
6FP6-F2H4-UCK7H
05QQ-M9EF-YBWBH
NMDN-E32M-18MWY
DAP8-MN04-P2P9A
Liu Kang Ghost
1NVA-VZAA-0857D
RBW1-ADJ0-10HP5
DXCM-EK4D-3KCAX
M2HT-A87Y-UEJEK
WA2Y-WU34-M4W73
Kira
3DRV-GMEB-BXK41
7R36-MHBH-E50M7
VA2M-NXHV-ZE999
6JHH-JNHZ-Z9VQ2
72UV-CV5U-ZXEZN
Kabal
TJQP-697R-2NEVH
H2P8-HN08-G1N8D
784K-1ZRT-6NNYP
3X1X-02NN-87UN5
D7XF-FHPX-TK87G
Kobra
XHTT-KBU5-XHX6P
TNDM-BBW6-3TJ2Y
DQU4-F7GK-1F1HV
RHHK-2A3H-AVHVQ
TZ30-8ZR0-91NAX
Jade
T8F2-MQ0P-TBUCD
N0QZ-EDVY-1CNK4
DUDZ-59U8-04RW5
CN4R-3RWJ-6C7V3
566J-H1UD-UE5AW
Dairou
ZWW1-QTFU-YWYEJ
5D51-R4PE-B3N2C
NZNB-9RDX-5W1EJ
ADRM-HDEJ-X51ZK
RY12-3KVG-7QJVE
Raiden
1W4P-V8UG-4HJ6R
P47Q-PY77-722H8
DCU3-0UMC-B1JAP
T8J2-Z901-VVJZM
FW3J-EXC0-P364M
Darius
VZ5K-1RGW-93P69
K955-6R6M-GV1FT
BFHU-788J-79YX5
546F-89MU-96ZR6
58HX-PPU2-BX786
Shunjiko
GKRY-U1N2-HRTWM
EDGB-PC9X-673CM
4QQ3-4P29-K961M
U8XJ-2354-YH57D
2X1C-PVUW-29ZFG
Shunjiko 13
YBEJ-UHK9-1RDXR
EDGB-PC9X-673CM
46KF-3CB4-1JBZP
0WY5-T3KD-Z8BD3
57C0-6G53-94X1M
Noob/Smoke
RZPC-M9BY-KRN1A
3C5N-YREP-7TGW1
V29Y-JYFA-B2CN5
2K2P-PD77-U2K8A
G171-RRH9-TR5CW
Monster/Freak
1TB7-D5P0-P953G
MRDD-BB3W-4QDRU
HJ93-9XZU-0CFW4
817Y-WJMJ-5NGVH
ZK8J-5JXJ-4TNP2
Onaga
VM1X-NU0P-YP8P2
7NWT-NZFV-D5BYM
PDK7-441U-JA0Y6
F38F-QEHU-87DTD
3YYV-EJXE-VT830
Jax
68ZM-2D44-P78J4
70QG-C188-1JGX8
CCKF-29VA-EG030
RHCV-C18K-XFARP
UZHQ-RZTT-DAQ7P
Old Rayden
Q661-3C8M-F7JT3
P47Q-PY77-722H8
EM9B-FKEV-K3AJG
PK5A-NYTE-Q4YRA
T488-NCAZ-4TC6M
QuanChi
F24H-6N05-G9R6H
H54G-MA0Y-Z9ZHV
Y4ZP-2CN8-FWWJQ
K4QQ-28UH-XJU27
BT02-7PZY-T2B5T
Kung Lao
HGKH-W29K-W5YJ9
XN43-X74C-R5VQQ
0NR4-F2AM-AFQD5
CG7D-YRXZ-N6747
NPVM-XQQ4-E8XAW
Johny Cage
4Y7E-6K7E-TR20X
0BUH-XNY7-0255E
NUWE-T7PV-BKCJT
8WAX-UG4N-AMJPN
J41E-C9QT-F8442
Sonya
C8XA-F855-JY56J
15GU-W5HU-X5KQ6
M276-JP31-XXMEB
J7GH-MDWC-19TWB
3WCK-XGR4-A3XRA
Nitara
1GFR-MCQC-K41J4
RYPJ-V8XW-W1A5D
JER5-B4AC-ZF194
2GXK-MV8F-Q52JN
ZCFE-2KEP-6DNKP
Shan Tsung
50MT-45TY-X847R
T9TA-7DWE-D88MU
9NXN-P45R-Y3BQ8
RNKE-ENDK-KZB7Z
1HCG-F7D3-FEP90
Frost
AKGA-48FK-P8TV5
NUXW-65RV-9YVHT
QGQ3-BB7H-TQPDU
9T2D-HRP6-HX9QX
PJNW-0WD8-4GYCF
Kitana
0KUC-XGHY-8RJW4
U3AV-C8DH-GGZPD
TP9G-HAMG-W0FJ7
JJBN-MRWJ-561RJ
YVXK-V0KV-THQMD
Drahmin
EG4U-NH1N-D8N6C
HX1T-K8HE-3VN0A
3P82-442J-A79Z0
2FVU-0E9J-G9AAH
121P-BH6E-1EF3Q

Is that true ?