I must confess that this story is a bit weird, but since we are in 2020, lets just enjoy it. (just a joke, sorry)
The story bellow, is a retelling of Castiel´s presentation on Lazarus Raising, but as the tittle and summary say, he isn´t 'human' but a 'dog'.
Lets suppose that in the fights scenes from the show, they use human actors (not only Misha Collins) but a lot of other actors or actress in any age, like they did with Lilith, but for most part, he was a GCI St. Bernard.
Other than that, the scenes from his first show up, are exactly the same.
Hope you like.
That evening, while Sam was in another part of the town with Ruby, Dean and Bobby settled everything to find the one creature, who earlier that same week, had let it clear it has taking Dean away from hell. This way, after making sure they were well prepared, the two men just set down and wait, when Dean took a deep breath.
''What is this creature?'' the younger hunter asked and in response, Bobby just laugh.
''Are you afraid?'' Bobby mocked, making Dean blush lightly.
''Of course not! You are sure you did the ritual right?''
''I did'' Bobby replied ''And It won't be as different as any other beast we have faced, Ya Idjit!''
As if on cue, a loud rattling shakes the roof. Dean and Bobby arm themselves with shotguns and take positions at the far end of the warehouse. The door bursts open and a second later, a gigantic dog resembling a St. Bernard, come in. It was Castiel
The light bulbs above his head shatter in a shower of sparks as he passes them. As he approaches, Dean and Bobby open fire, but the shots do not even slow the dog down. Furious, Dean takes the Magic Knife as Castiel gets close.
''What the hell are you?'' Yelled Dean.
''I'm the one who gripped you tight and raised you from perdition.'' The dog said simply in human´s voice.
''Yeah. Thanks for that.'' He said rearing back and plugging the knife into Castiel´s leg chest, but in response, the dog just look down, unconcerned, and pulls it out with his mouth and drops it to the floor.
Behind him, Bobby attacks; but without even looking, the dog grabs Bobby´s weapon and uses it to swing him around, then, he placed his front paws on his forehead and Bobby crumples to the ground.
''We need to talk, Dean. Alone.'' He said again, using a human's voice, as Dean crouches over Bobby cheking his pulse, not taking his eyes from Castiel.
''Your friend's alive.'' He said.
Upon hear the dog talking, Dean could help but be speechless. A dog was talking to him, for all the unnatural things he had seen in life, a talking dog, was the last expected.
''Who are you?'' the hunter asked angry and still perplexed.
''Yeah, I figured that much, I mean what are you?'' he mocked ''A new version of Scooby Doo?''
''I'm an Angel of the Lord.'' The deg replied and Dean looked at him furiously.
''Get the hell out of here. There's no such thing.''
''This is your problem, Dean. You have no faith.'' Castiel seemed disappointed, when suddenly, Lightning flashes and on Castiel´s back great shadowy wings appear, stretching off into the distance. The light goes out and the image disappears.
''Some angel you are. You burned out that poor woman's eyes.''
''I warned her not to spy on my true form. It can be... overwhelming to humans, and so can my real voice. But you already knew that.''
''You mean the gas station and the motel. That was you talking?'' Dean asked and in response, the angel nodded ''Buddy, next time, lower the volume.''
''That was my mistake. Certain people, special people, can perceive my true visage. I thought you would be one of them. I was wrong.'' He said making Dean laugh.
''And what visage are you in now, huh? Granny's lap dog?''
''This? This is... a vessel.'' The angel explain, looking down at his own body.
''You're possessing some cute puppy?''
''Oh, no, this… this dog was dying and he actually prayed for this, Dogs are also very devoted, you know?''
''Well, I'm not buying what you're selling, I must be high or something, if you aren't just a talking dog, who are you really?'' he asked and for the first time, the dog growled, showi g Dean his sharp fangs.
''I told you'' he snarled.
''Right. And why would an angel rescue me from Hell?''
''Good things do happen, Dean.''
''Not in my experience.'' Dean replied and in response, Castiel give him a sad look.
''What's the matter? You don't think you deserve to be saved?''
Just answer why'd you do it?'' he asked and in response Castiel approach him with a serious look.
''Because God commanded it. Because we have work for you.'' the angel said finally, leaving Dean speechless again once and for all.