You're as mindless and obedient as an attack dog. (Dream Dean, about Dean, 3x10)
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DEAN: So you sic your attack dog on us to what, say hi? (Dean, about Toni Bevell, 12x02)
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ROWENA: Attack-dog spell. We needed a decoy.
CAITLIN: But... But she'll die, just like the waiter. ROWENA: Probably. Few humans are built to survive magic like that, and Elle was weak. But you're not.
10x07
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CAS: It appears I simply respond differently from humans.
DEAN TO CAS: If you were you human, you'd be gone. With you, it's like it's digging deeper.
11x03
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SAM: Okay. So, a Shojo is said to roam where there's lots of alcohol. ... Apparently, you can harness the will of a Shojo with the right spell box. Then you basically have an attack dog that you can sic on whatever sort of personal revenge mission you want. (SAM, about the monster of the week, 7x18)
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DEAN: And that's...? (SOULLESS) SAM: Dog's blood.
DEAN: Do I even want to know where you got that?
6x06
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The dog trots after JEFFREY carrying the plastic cone.
DEAN: No. The dog yelps.
DEAN: Oh, you sick son of a bitch.
The plastic cone rolls into sight. JEFFREY places the bowl, which now contains one of the dog’s organs, on the coals, then adds DEAN’s blood.
7x15
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CHEF LEO: Why does it smell like dog in here? (He turns and sees DEAN.) That smell's coming from you. ...
DEAN: Do you really think the power you hold over other people's lives can make up for what you lack in your own?
CHEF LEO: So, dog boy, what do I need to eat to take you down, huh? Ah. [He holds up a container labelled “Wolf Heart.”] Dog on sort-of dog. ... Sorry. Wolf trumps dog.
9x05
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DEAN: I don't know. I mean, Cas is kind of like a talking dog...
&
DEAN: "being" SCOOBY: Scooby dooby dooooo! CAS: Dean, you're not a talking dog. 13x16
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SAM: Just leave me alone.
VISION!DEAN (Sam's subconscious): Makes you feel strong. Invincible. A big bad wolf in a world of little pigs.
4x21
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And there's something about Dean "becoming like a dog" and Cas getting cursed with the attack-dog spell and Jack turning INTO a dog... hmmm.