[quote:133b041f95]The 'see pkmn graphics' menu. You can view all the pokemon and even edit their palettes. Oddly enough pokemon 252-276 are missing (treecko is 277). Removed pokemon perhaps? I wonder if they're still in the rom somewhere. [/quote:133b041f95]

This has been known about for some time now. In the final version, this thing appears when you force data from any of those slots to appear: 

http://bulbapedia.bulbagarden.net/wiki/%3F_%28glitch_Pok%C3%A9mon%29

Its actually a beta version of the sprites used for unidentified pokemon in the pokedex. 

The one in the final version of course uses this sprite:
http://bulbapedia.bulbagarden.net/wiki/Ten_question_marks
Which is also a glitch pokemon in the final that occupies hex slots 00 and everything 19B and beyond.