a twinkle in someone's eye

twinkle in (one's) eye

1. A facial expression that denotes happiness, amusement, or knowledge of a secret. Just when Rita thought all hope was lost, Jared got a twinkle in his eye that told her he had a plan to get them both out of that sticky situation.
2. A hope or plan that is not yet in existence. You were not even a twinkle in your mother's eye when that photo was taken.
See also: eye, twinkle
Farlex Dictionary of Idioms.

a twinkle in someone's eye

or

a gleam in someone's eye

If a plan or project is only a twinkle in or a gleam in someone's eye, it is only at the stage of being considered as a possibility. Projects that a few years back were just a twinkle in the planners' eyes are now bricks and cement. At this point, space-launched weapons were still only a gleam in his eye. Note: You can also talk about a glint in someone's eye. The European central bank was still no more than a glint in its creators' eyes. Note: Words such as gleam, glint and twinkle can be used to describe the way people's eyes shine or reflect the light. They often suggest hidden energy, emotion, or humour and refer to the excitement of having a particular idea before putting it into practice.
See also: eye, twinkle
Collins COBUILD Idioms Dictionary, 3rd ed.

a twinkle in someone's eye

something that is still in the pre-planning stage and on which no action has yet been taken, especially a child not as yet conceived. informal
See also: eye, twinkle
Farlex Partner Idioms Dictionary
See also:
  • twinkle in (one's) eye
  • a gleam in someone's eye
  • gleam
  • gleam in (one's) eye
  • when (one) was a twinkle in (one's) father's eye
  • twinkle in (one's) father's eye
  • make a face
  • make a face (at someone)
  • in the twinkle of an eye
  • when (one) was a twinkle in (one's) daddy's eye
References in periodicals archive
A twinkle in someone's eye tells you they are more interested than sticking around than taking the last bus home but are you so up for it?
A twinkle in someone's eye. I say no more than that."