I made a skin based on the "GHOST" found in Pokemon Red/Blue/Yellow.

You could get a MissingNo. Glitch Pokemon that looked like the ghost, also, by doing the "Old Man Glitch".However, in Yellow version, that glitch was not possible, so you had to do it using the Mew glitch.(Google the glitches.)They were possible without a Gameshark, same with a lot of other glitches.The Ghost was really strong, however the MissingNo. Ghost in Yellow would be Lvl. 7, so you had to train it.

The Ghost in Pokemon Tower in Lavender Town cannot be caught, but if you have the Silph Scope, the Ghost will be revealed to be a Gastly or other pokemon in the tower.You can probably have a real Ghost if you have a Gameshark, not sure.

This is a HD Version of the skin, being 128 in Width and 64 in Height: