In DISNEYLAND it is not uncommon to hear someone refer to a character by a nickname. ie. Spieling Peter. This tradition has stayed out of Walt Disney World on the overall. The problem with this happening at Walt Disney World is that there are many people who visit and if every person who meets that character gives them a nickname there will be more nicknames for the character than they have friends.
This is an example of two different guests visiting peter on the same day…
See the Problem with this. To many lovely guests meeting the wonderful Peter Pan.
I think that if you have your own nickname for characters that is your right but I think that for everyone sake include the characters you should probably refer to them by their official name that they sign in your autograph book. Just a thought.