The Japanese version of Pokémon Crystal used to be part of a system known as Mobile System GB that was discontinued in December 2002. Features from the system could be accessed via the title screen, Battle Tower and a special Pokémon Center called the Pokémon Communication Center (which was replaced with a regular Pokémon Center in the English version). Players could connect a Game Boy Color or Game Boy Advance to the service using a mobile phone and the Mobile GB Adapter. The Japanese version of Pokémon Crystal supported features such as online battles with other players, online trades, exchanging Battle Tower data, and access to news via the "Pokémon News Machine". Using arbitrary code execution, we can obtain a Mobile Trade Celebi in your party (based on an online trade 'partner found' feature) the next time you visit the Pokémon Communication Center. This Pokémon is added to the Pokédex. Steps:. 1) Play Japanese Crystal normally up to Goldenrod City. Pick up Kurt's Lure Ball and make it your only Poké Ball after catching a second Pokémon. The second Pokémon should be Abra if possible, so you can Teleport to the PCC Center to avoid Trainers north of Goldenrod after Missingning takes us into the north-east Bug-Catching Contest building. |--| 2) Perform Crystal Pokémon cloning (where you deposit a Pokémon, switch boxes and reset the game shortly after the save message is printed) and create five clones of your starter. 3) Deposit the clones into box 3. Get corrupted clones (consisting of "?" marks in their names) by resetting the game at a very precise time. You will need to withdraw a bad clone; which is a Pokémon that may be at level 1 when withdrawn, is the opposite gender to the original Pokémon (not always) and will convert into a ????. (00) when taken into the Day Care and out. |--| 4) Have five Pokémon in your party including the bad clone, and withdraw the bad clone. Turn it into a hex:00 ????. by taking it into the Day Care and out. |--| 5) Put the ????. hex:00 in slot 1 of the party. Use "Move PkMn w/o Mail" to place a seventh Pokémon in slot 1, and deposit the ????. in slot 2 into the Day Care. It should now become a hex:FF when you withdraw it. |--| 6) Deposit a Pokémon to make space for hex:FF, and withdraw it. |--| 7) Enter Goldenrod PCC Center, do Missingning five steps right of Goldenrod PCC Center door (so it is just off the screen) to warp to the north-east Bug Catching Contest building. Your items should be corrupted too. Note that other Missingnings may not warp you, or give you the wrong items. |--| 8) Step out of the contest building and back in to avoid a possible freeze when you open the bag and close it. |--| 9) Deposit a TM01 into PC from glitched TM/HM pocket inventory as well as TM15 x195. |--| 10) In regular items pocket, swap TM38 into. x0 (corrupts key items pocket) (note: other swaps may work too). 11) In Key Items pocket, swap first. x0 with. x1 (above Kurt's ball) (note: other swaps may work too). |--| Ball ID becomes number of balls and you will receive Master Ball x255. |--| 12) Move the TM01 up to the first balls slot. |--| 13) In Key Items pocket do step 11 again to get 191 (TM01's index number) balls. |--| 14) Deposit 251 Star Pieces from the items pocket into the PC. |--| 15) The TM15 x195 and Star Piece x251 will appear in the glitched balls pocket. Swap them into the right place (Pokégear may disappear). You can place the TM15 x195 in the right place by pressing up exactly 29 times from the bottom of the Balls pocket. After that, you can place the Star Piece x251 in the slot below it. The bytes will shift meaning you have to swap the TM15 x195 an extra slot down after the switch. |--| 16) Deposit your Pokémon and withdraw Abra, make sure you have 5 or less including Abra, and Teleport back to Goldenrod with Abra (otherwise you'll probably have to walk it). 17) Enter the Poké Communications Center, and write the following box names. Box 4: ョぼガがパぜパづ. Box 5: ぼザがゼづぼガベ. Box 6: がロぜガずずずず. Box 7: ずづョべべべべべ. Box 8: がロぜがづがィ. Box 9: ぜだづの. 18) Use the TM15 in the Balls Pocket and close the menu to obtain a level 2 Celebi with 16449536 experience with an OT of ?????, ID of 00000, and no known moves (although it can learn more by levelling up and through TMs and HMs. The "Missingning" trick gives us many amounts of every TM and HM. Technical information about the code execution and data structure of the obtained Pokémon.