Noun: "(idiomatic, colloquial, humorous) a notional look of anticipation or hope (either for sex or a child) in one's father's eyes at or around the time of one's conception"
One is getting to the boiling fowl stage when one can remember having one's palm read by Gipsy Sarah on the sandhills before the modern South Shore took shape; and before you, Mr. Mayor, were a twinkle in your father's eye.
"Look, I lived in this town while you were still a twinkle in your father's eye[…]
1975, Terry Blake, The Fig Tree, Aim Publishing (1975), page 26:
Kimberly handed him a whisky and said: "So's that, my boy. Forty-eight-year-old Glenlivet. This was a connoisseur's drop before you were a twinkle in your father's eye."
'Don't you take the piss out of me, sonny. I was doing this job when you were just a drunken twinkle in your father's eye!'
2010, Max Overton & Jim Darley, Sequestered, Sequestered Books (2010), →ISBN, unnumbered page:
“Thirty years ago you would not even have been a twinkle in your father's eye.”
2012, J. D. Hallowell, Dragon Blade: War of the Blades, Smithcraft Press (2012), →ISBN, unnumbered page:
“I passed my ninetieth birthday nearly fifty years ago,” Nat replied. “Furthermore, I have been studying medicine since before you were even a twinkle in your father's eye, old wizard.”
2012, Sally McDermott, The Curious Caves of Honey Cove, iUniverse (2012), →ISBN, page 118:
“Murder? Unlucky people have been drowning at that stretch of sea since long before you were a twinkle in your father's eye. Just forget it.”