Source: geocities.com/pokemon251us2000

Game Genie code to get Mew:

(I do not have a Game Genie to test this out, so I'm not sure if it 
works.)

151-91A-7FC
151-93A-F7E
B91-9BA-6EB


Gameshark Code for Mew (RED & BLUE):

The code for Mew is 0115D8CF
(Don't have a Gameshark either. So I can't confirm)
*****************************************************************************
Game Genie codes 
WARNING:These may erase your saved game! 
MEW CODE (American version) 
for pokemon red + blue:151-91a-7fc/ 151-93a-f7e/ 151-9ba-5db Now, look left 
of Cerulean City in the grass. It will take a few tries but eventually you 
will see him. WARNING!!: If he uses TRANSFORM and you catch him you WILL 
catch a Ditto. So put him to sleep, hit him quickly, then get him! Now link 
up with a friend for a fight and make em say Oooh! 

GET RICH QUICK
If you put in 996-11b-e6a, it will make a POKEBALL worth $990200! 

Fight missingno
TYPE in 001-91a-7fc+001-93a-f7e+001-9ba-5db
*****************************************************************************
NOTE: These codes have been tested and work. Please do not steal these! 
Thanks.

Infinite Money:

019946D3
019947D3
019948D3

Enemy Pokémon Are Always Affected By Burn & Sleep: (NOTE)

0115E8CF

This code affects wild Pokémon and your opponent's Pokémon. This code never
wears off and your Pokémon are virtually INVINCIBLE!

Infinite Health:

01??15D0

Buy Any Item:

01??7BCF

Item Quantity Digits: (The ??'s)

01 - Master Ball     0
02 - Ultra Ball   1200
03 - Great Ball    200
04 - PokéBall      200
05 - Town Map        0
06 - Bicycle         0
08 - Safari Ball     0
09 - Pokédex         0
0A - Moon Stone      0
0B - Antidote       100
0C - Burn Heal      250
0D - Ice Heal       250
0E - Awakening      200
0F - Parlyz Heal    200
10 - Full Restore  3000
11 - Max Potion    2500
12 - Hyper Potion  1500
13 - Super Potion   700
14 - Potion         300
1D - Escape Rope    550
1E - Repel          350
1F - Old Amber        0
20 - Fire Stone    2100
21 - Thunder Stone 2100
22 - Water Stone   2100
23 - HP Up         9800
24 - Protein       9800
25 - Iron          9800
26 - Carbos        9800
27 - Calcium       9800
28 - Rare Candy    4800
29 - Dome Fossil      0
2A - Helix Fossil     0
2B - Secret Key       0
2D - Bike Voucher     0
2E - X Accuracy     950
2F - Leaf Stone    2100
30 - Card Key         0
31 - Nugget       10000
32 - PP UP         9800
33 - PokéDoll      1000
34 - Full Heal      600
35 - Revive        1500
36 - Max Revive    4000
37 - Gaurd Spec     700
38 - Super Repel    500
39 - Max Repel      700
3A - Dire Hit       650
3B - Coin            10
3C - Fresh Water    200
3D - Soda Pop       300
3E - Lemonade       350
3F - S.S. Ticket      0
40 - Gold Teeth       0
41 - X Attack       500
42 - X Defend       550
43 - X Speed        350
44 - X Special      350
45 - Coin Case        0
46 - Oak's Parcel     0
47 - Item Finder      0
48 - Silph Scope      0
49 - PokéFlute        0
4A - Lift Key         0
4B - Exp. All         0
4C - Old Rod          0
4D - Good Rod         0
4E - Super Rod        0
4F - PP Up            0
50 - Ether            0
51 - Max Ether        0
52 - Elixer           0
53 - Max Elixer       0
C4 - HM01 Cut         10104
C5 - HM02 Fly         10104
C6 - HM03 Surf        10104
C7 - HM04 Strength    10104
C8 - HM05 Flash       10104
C9 - TM01 Mega Punch   3000
CA - TM02 Razor Wind   2000
CB - TM03 Swords Dance 2000
CC - TM04 Whirlwind    1000
CD - TM05 Mega Kick    3000
CE - TM06 Toxic        4000
CF - TM07 Horn Drill   2000
D0 - TM08 Body Slam    4000
D1 - TM09 Take Down    3000
D2 - TM10 Double-Edge  4000
D3 - TM11 Bubble Beam  2000
D4 - TM12 Water Gun    1000
D5 - TM13 Ice Beam     4000
D6 - TM14 Blizzard     5000
D7 - TM15 Hyper Beam   5000
D8 - TM16 Pay Day      5000
D9 - TM17 Submission   3000
DA - TM18 Counter      2000
DB - TM19 Seismic Toss 3000
DC - TM20 Rage         2000
DD - TM21 Mega Drian   5000
DE - TM22 Solar Beam   5000
DF - TM23 Dragon Rage  5000
E0 - TM24 Thunderbolt  2000
E1 - TM25 Thunder      5000
E2 - TM26 Earthquake   4000
E3 - TM27 Fissure      5000
E4 - TM28 Dig          2000
E5 - TM29 Psychic      4000
E6 - TM30 Teleport     1000
E7 - TM31 Mimc         2000
E8 - TM32 Double Team  1000
E9 - TM33 Reflect      1000
EA - TM34 Bide         2000
EB - TM35 Metronome    4000
EC - TM36 Selfdestruct 2000
ED - TM37 Egg Bomb     2000
EE - TM38 Fire Blast   2000
EF - TM39 Swift        2000
F0 - TM40 Skull Bash   2000
F1 - TM41 Softboiled   4000
F2 - TM42 Dreameater   2000
F3 - TM43 Sky Attack   5000
F4 - TM44 Rest         2000
F5 - TM45 Thunder Wave 2000
F6 - TM46 Psywave      4000
F7 - TM47 Explosion    3000
F8 - TM48 Rock Slide   4000
F9 - TM49 Tri Attack   4000
FA - TM50 Substitue    2000
FB - TM51 Cut             0
FC - TM52 Fly             0
FD - TM53 Surf            0
FE - TM54 Strength        0
FF - TM55 Flash           0

Ability Quantity Digits: (The ??'s)

*****************************************************************************
Fight Any Pokémon:

For YELLOW:	01??D7CF
For RED & BLUE:	0115D8CF

Bulbasaur -   99
Ivysaur -     09
Venusaur -    9A
Charmander -  B0
Charmeleon -  B2
Charizard -   B4
Squirtle -    B1
Wartortle -   BC
Blastoise -   1C
Caterpie -    7B
Metapod -     7C
Butterfree -  7D
Weedle -      70
Kakuna -      71
Beedrill -    72
Pidgey -      24
Pidgeotto -   96
Pidgeot -     97
Rattata -     A5
Raticate -    A6
Spearow -     05
Fearow -      23
Ekans -       6C
Arbok -       2D
Pikachu -     54
Raichu -      55
Sandshrew -   60
Sandslash -   61
Nidoran F -   0F
Nindorina -   A8
Nidoqueen -   10
Nidoran M -   03
Nindorino -   A7
Nidoking -    07
Clefairy -    04
Clefable -    8E
Vulpix -      52
Ninetales -   53
Jigglypuff -  64
Wigglytuff -  65
Zubat -       6B
Golbat -      82
Oddish -      B9
Gloom -       BA
Vileplume -   BB
Paras -       6D
Parasect -    2E
Venonat -     41
Venomoth -    77
Diglett -     3B
Dugtrio -     76
Meowth -      4D
Persian -     90
Psyduck -     2F
Golduck -     80
Mankey -      39
Primeape -    75
Growlithe -   21
Arcanine -    14
Poliwag -     47
Poliwhirl -   6E
Poliwrath -   6F
Abra -        94
Kadabra -     26
Alakazam -    95
Machop -      6A
Machoke -     29
Machamp -     7E
Bellsprout -  BC
Weepinbell -  BD
Victreebell - BE
Tentacool -   18
Tentacruel -  9B
Geodude -     A9
Graveler -    27
Golem -       31
Ponyta -      A3
Rapidash -    A4
Slowpoke -    25
Slowbro -     08
Magnemite -   AD
Magneton -    36
Farfetch'd -  40
Doduo -       46
Dodrio -      74
Seel -        3A
Dewgong -     78
Grimer -      0D
Muk -         88
Shellder -    17
Cloyster -    8B
Gastly -      19
Haunter -     93
Gengar -      0E
Onix -        22
Drowzee -     30
Hypno -       81
Krabby -      4E
Kingler -     8A
Voltorb -     06
Electrode -   8D
Exeggcute -   0C
Exeggutor -   0A
Cubone -      11
Marowak -     91
Hitmonlee -   2B
Hitmonchan -  2C
Lickitung -   0B
Koffing -     37
Weezing -     8F
Rhyhorn -     12
Rhydon -      01
Chansey -     28
Tangela -     1E
Kangaskhan -  02
Horsea -      5C
Seadra -      5D
Goldeen -     9D
Seaking -     9E
Staryu -      1B
Starmie -     98
Mr. Mime -    2A
Scyther -     1A
Jynx -        48
Electabuzz -  35
Magmar -      33
Pinsir -      1D
Tauros -      3C
Magikarp -    85
Gyarados -    16
Lapras -      13
Ditto -       4C
Eevee -       66
Vaporeon -    69
Jolteon -     68
Flareon -     67
Porygon -     AA
Omanyte -     62
Omastar -     63
Kabuto -      5A
Kabutops -    5B
Aerodactyl -  AB
Snorlax -     84
Articuno -    4A
Zapdos -      4B
Moltres -     49
Dratini -     58
Dragonair -   59
Dragonite -   42
Mewtwo -      83
Mew -         15