1. Let's start at the very beginning. Remember the dead direwolf that had been killed by a stag in the first episode?
2. And the whole thing didn't end too well for the stag, either.
3. And that's not the only time we see real animals used as analogies for the houses of Westeros.
4. Also, in this deleted scene from Season 3, we see Tywin expertly catching and killing some fish.
Which house's sigil is a fish? House Tully. And who is one of the (many) people who meets a bloody end on the orders of Tywin Lannister at the end of Season 3? Catelyn Stark (neé Tully).
As the scene was deleted, this one may hold a little less weight, though it was probably deleted only due to its length. You can watch the scene in full here – look out for Grand Maester Pycelle's moment of uncharacteristic honesty.