About 20 years ago, I was the shaliach tzibbur in a shul in Newburgh, NY on Yom Kippur. As I was davening, I hear behind me, "jingle, jingle". I turn around, and behold, there is a man dressed in a long white robe with gold trim, a "breast plate" with colored stones on it, and the bottom of the robe had "pomegranates" and bells. In other words, he was dressed like the Kohen Gadol!
When he got the Kohen aliyah, I verified that he was a Kohen.
I didn't have a chance to ask him why he was wearing his "outfit", as I didn't want to embarrass him. (some people were laughing at him, and he may have been conscious of that.) I'm curious if there is any minhag anywhere for a Kohen to dress this way on Yom Kippur, or was this guy just dressing this way on his own "whim"?