The spoken use of "night" as an informal, familiar version of "good night" (wishing one a restful sleep) is common, but I'm not sure what the proper written equivalent is - if there is one. I have always used 'Night with an apostrophe, usually capitalized:
Is any form of "night" for "good night" (with or without an apostrophe) correct as used in my example? I read a lot of Walt Kelly growing up so that may be why I use it.
I don't see a reason to use the apostrophe, as I'm not using "G'Night", with or without capitalization.
Are there different rules when conveying informal speech in writing?