are you kidding me, it has to hold a freaking item to become ghost
Ok then other than Kitsunoh which only exists in smogon land there are no quadrupedal ghost types. Thus rendering your topic moot. There have been two answers given and you waved them away with weak excuses.
That is every ghost type that exists in the games. Take 3 seconds to look over it and you will see that other than the two examples already given there are none.
Either give the Celebi to the guy who said Rotom or the first guy who said Arceus. Assuming you even had it. Granted I'm sure one could easily take a few seconds and hack one in. --- http://tinyurl.com/ck8fqvn http://tinyurl.com/kwzh647