1(Supernatural)

An Au where Castiel is technically the child of the four archangels, the archangels were never in a relationship but Chuck(God) created him using the four archangels essence and then had the four of them raise him.

They did their best as one things was being a big siblings to all the other angels and another was being a parent to one angel that could be as calm as Raphael and Michael in a second in the another be a hurricane like Lucifer and Gabriel.

Things went down similar to canon on Lucifer falling, God and Gabriel leaving, Naomi being given the task of taking care of the angels(but instead forcing them to become emotionless), etc.

But when it came to Castiel fighting any angel, the other angels would find themselves unable to hurt him with an angel blade as he could only be hurt by an archangel one besides the archangels never bringing him to the middle of their fight as it was Naomi and Metraton that gave Castiel the task of raising Dean from hell.

Anything else is up to the writer but there needs to be a scene when Gabriel appears that Castiel goes like 'Hi, dad' and Gabriel goes 'Hey, Cassie' before realizing he gave himself up for that or the Winchesters and other hunters finding out that Castiel is equal to an archangel as he is technically the child of the four archangels.

Also, imagine the other Michael discovering that unlike his universe, Castiel wasn't one of his many siblings but technically is child which in certain terms could be said that him and the other archangels spoiled.