twinkle in one's father's eye

Noun

 * 1)  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.
 * 2) * 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."

Usage notes
Used to refer to a person when discussing things which existed at or before the time that person was conceived.