goo-goo eyes
A visibly smitten or enamored facial expression, as of one who is romantically interested in someone else. Well, if you keep staring at her with goo-goo eyes, she'll know you like her sooner than later!
make goo-goo eyes at (someone)
To look at someone with an enamored or flirtatious expression. Often said of two people who romantically interested in each other. Those two have been making goo-goo eyes at each other all night—it's so nauseating for those of us who are single. Well, if you keep making goo-goo eyes at her, she'll know you like her sooner than later!