(one's) eyes pop out of (one's) head
One's facial expression indicates surprise. Often modified with words like "practically" or "nearly" after the word "eyes." My eyes practically popped out of my head when I saw that my parents had bought me a car for my birthday!
your eyes nearly pop out of your ˈhead
(informal) somebody has an expression of great surprise on their face: Our eyes nearly popped out of our heads when we saw a giraffe walking down the High Street. ▶ ˈeye-popping adj. (informal) very surprising or amazing: a movie with eye-popping special effects