Pae (o Mae) Coruja is the original phrase. This comes from the french folktale by Jean de la Fontaine, that later was brought to Brazil most likely via Portuguese.
In the tale an owl mother describes her babies to an Eagle in an agreement to not eat each others children: It refers to the tendency of a parent to see only the beauty in her children, in other words, a mother, and fathers, tend to focus on the positive in their children. In English we do have a related saying "He/She has a face only a mother could love". "Love is blind," could also be seen as related. "beauty is in the eye of the beholder". Mae coruja can currently be used for any parent who sees their child as extraordinary. For example, a mother is cheering her child on at a soccer game, telling her that she is fantastic and just in the right position, and someone might jokingly comment "Mae Coruja!"
The eagle and the owl, resolved to cease
Their war, embraced in pledge of peace.
On faith of king, on faith of owl, they swore
That they would eat each other's chicks no more.
"But know you mine?" said Wisdom's bird.
"Not I, indeed," the eagle cried.
"The worse for that," the owl replied:
"I fear your oath's a useless word;
I fear that you, as king, will not
Consider duly who or what:
You kings and gods, of what's before you,
Are apt to make one category.
Adieu, my young, if you should meet them!"
"Describe them, then, or let me greet them,
And, on my life, I will not eat them,"
The eagle said. The owl replied:
"My little ones, I say with pride,
For grace of form cannot be matched,
The prettiest birds that ever were hatched;
By this you cannot fail to know them;
It's needless, therefore, that I show them.
Pray don't forget, but keep this mark in view,
Lest fate should curse my happy nest by you."
At length God gives the owl a set of heirs,
And while at early eve abroad he fares,
In quest of birds and mice for food,
Our eagle haply spies the brood,
As on some craggy rock they sprawl,
Or nestle in some ruined wall,
(But which it matters not at all,)
And thinks them ugly little frights,
Grim, sad, with voice like shrieking sprites.
"These chicks," says he, "with looks almost infernal,
Can't be the darlings of our friend nocturnal.
I'll sup of them." And so he did, not slightly:
He never sups, if he can help it, lightly.
The owl returned; and, sad, he found
Nothing left but claws on the ground.
He prayed the gods above and gods below
To smite the brigand who had caused his woe.
Said one, "On you alone the blame must fall;
Or rather on the law of nature,
Which wills that every earthly creature
Shall think its like the loveliest of all.
You told the eagle of your young ones' graces;
You gave the picture of their faces:
Had it of likeness any traces?"
Jean de La Fontaine
Book 5, Fable 18
Source: http://www.musee-jean-de-la-fontaine.fr ... uk-24.html