Wiktionary
a. (context simile English) Extremely proud.
Wikipedia
"Proud as a Peacock" was the advertising campaign used by the NBC television and radio networks from 1979-1981. The campaign was used to promote NBC's programming and to introduce the "Proud N", a logo that would be used until 1986.
Usage examples of "proud as a peacock".
Tonga thought he had done something very clever in killing him, for when I came up by the rope I found him strutting about as proud as a peacock.
Some human mechanician, I daresay, eager to please the vampire lords and ladies, showed off his cleverness as proud as a peacock.
Isobel spun about to find Beckett smiling at her, proud as a peacock.
The judge peeked around the corner to make certain everyone was standing, then strutted into the courtroom, looking as pleased and proud as a peacock.