✔ 最佳答案
There is no apostrophe after 'Hey', there IS a comma.
'Hey! Guy.' are really 2 slang greetings and both are in bad taste (manners AND English).
'Hey Guy.' is a slang greeting but less aggravating than the above one.
'Hey, guy.' is a slang greeting also but the speaker took a quick rest between Hey and guy.
If you MUST respond to such a greeting, simply say, "Whajja want, ya bum, ain't ya gots no manners?"
;-)