MissingNo.
Pokemon #000
Type: Same as last Pokemon in party
Hex Value: B7
Starting Moves: Same starting moves as last Pokemon viewed, but may change

Fossil MissingNo is encountered by Surfing along the east coast of Cinnabar Island after watching the Old Man's demonstration. Unlike other forms of MissingNo, this one has the image of the Aerodactyl Fossil from the Pewter City Museum. This MissingNo is found only if you have a "x" in the 3rd, 5th, of 7th slot of your name (making it highly unlikely to accidentally encounter this glitch). Once you catch this MissingNo it will no longer have the fossil graphic. Fossil MissingNo can also be encountered by perfoming the extended Mew Trick using a Pokemon with a Special stat of 183.

Unlike the standard pixel MissingNo, this glitch takes its moves from the starting form of the last Pokemon you viewed. For instance, if you looked at a Ditto's stats before encountering it, the Fossil MissingNo would know Transform. If you haven't looked at any Pokemon since loading your game, Fossil MissingNo will use the starting moves from whatever Pokemon was on your title screen when you pressed Start.

Fossil MissingNo's moves can change after the battle. It is not clear why this happens. Fossil MissingNo's type will change to match whatever Pokemon in last in your party. Additionally, you can make Fossil MissingNo learn any TM or HM move by placing a Pokemon that can learn the desired TM/HM in the last spot of your party.

When training a MissingNo at a high level (determined by other letters in your name), this glitch will increase and decrease levels randomly. For example, you catch MissingNo at level 163. After gaining any experience, it will "grow" to level 100. Then it may jump down to level 70. Its stats will randomly change (sometimes drastically) after it changes level.

In Pokemon Stadium, MissingNo will appear as a baby Rhydon Substitute doll. It will not be able to participate in any Stadium battles (the Pokemon will appear grayed-out). In Stadium 2, it will appear as a Ditto (at level 100, if it had been over level 100) knowing Transform. If you view a MissingNo in Stadium 2, it will permanently become a Ditto on your saved game.

MissingNo does not make your game save when you encounter it. Although a MissingNo will corrupt your Hall of Fame records, it won't do as much damage to them as 'M will.

Battling with MissingNo can cause your game's graphics to be temporarily scrambled during battles. Wild Pokemon may face away from you, mirror-imaged. When you register a hit on an enemy Pokemon, the image may break into scrambled vertical lines of the enemy. Your trainer's sprite viewed through the menu looks like a scrambled Brock.

MissingNo causes the 6th item in your held inventory to be increased by 128. This is a great way to get more evolution stones, Master Balls, Full Restores, and other expensive goodies.

Screenshots (courtesy of Teresa):

Next: MissingNo (Kabutops Fossil)