"Sunny side up" is a cheerful and poetic way to describe an egg fried on one side, with the yolk left unbroken and shining up at you. Or is it staring up at you? Reflecting up at you? There is more than one image suggested by a half fried egg, and different languages have settled on different ideas of what this egg looks like.
In Japanese, a sunny side up egg is a medama yaki, or fried eyeball. Hebrew and Romanian also call them eye eggs. They do just stare up at you, unblinking.
A COW'S EYE
In Malaysian and Indonesian, it's telur mata sapi, or cow's eye egg. In Italian, sunny side up eggs are also cow's eyes, or uovo all'occhio di bue. Not only is your breakfast looking at you, but it is doing so with the gentle, limpid gaze of a cow.
In German, it's a Spiegelei, or mirror egg. Danish, Norwegian, Dutch, and Hungarian also take this approach, which focuses on the shiny, reflective surface of the gently cooked egg.
When you crack an egg onto a surface, the edges might expand in irregular projections, like a star. In Thai, it's called kai dow, or star egg. Mexican Spanish also uses huevos estrellados for these surface cooked eggs.
See a collection of fried egg terms put together by Ayuho Uchida here.