The word chanyeol-eyed comes from a video, where a bulbous eyed multitalented kpop idol, the English legend, Park Chanyeol was flappergasted by something.
In general you can use the chanyeol-eyed when someone is taken aback, amazed or indeed flabbergasted.
I was chanyeol-eyed when I heard about EXOs comeback.
Janet was chanyeol-eyed when she found out that she had passed all the exams.