des yeux de merlan frit

To look lovesick

This expression describes rolling one's eyes back to show the whites, making a naive or lovestruck look.

Arrête de lui faire des yeux de merlan frit, c'est embarrassant !

Stop making puppy-dog eyes at them, it's embarrassing!

Replaced an earlier version, 'yeux de carpe frite' (fried carp eyes), in the 19th century. Fried fish have bulging white eyes that look a bit like someone rolling their eyes back in a lovesick daze. Silent cinema's exaggerated expressions helped popularise it.