[{"breed":"Akita","origin":"Japan","url":"https://en.wikipedia.org/wiki/Akita_(dog)","img":"some img url","WikiDescr":[{"contenido":"Content"}],"Behavior":[{"good_with_children":3,"good_with_other_dogs":1,}]}]

db.collection.aggregate([{"$unwind":"$Behavior"},{"$replaceRoot":{"newRoot":{"$mergeObjects":["$$ROOT","$Behavior"]}}},{"$project":{"Behavior":0}},{"$out":"coll1"}])