Considering how far genetics has come and that's just the stuff publicly available it isn't hard to believe that they could manufacture "real aliens" either so it could be possible that we do see them but we likely won't be allowed to do tests on them or the hoax would be found when the aliens are shown to be chimeras of earth creatures genetically.
Considering how far genetics has come and that's just the stuff publicly available it isn't hard to believe that they could manufacture "real aliens" either so it could be possible that we do see them but we likely won't be allowed to do tests on them or the hoax would be found when the aliens are shown to be chimeras of earth creatures genetically.
That genetic hybrid thing happened on Earth once before between humans and... not humans. God was so mad about it Noah had to build a boat.
See: Genesis 6