There is a weiner dog store in Portland that also operates a Doxen rescue mission. I asked the lady what they were rescuing them from and she had a crazy story about how aggressive they can become and that most doxens that have kids introduced after they've been with the family will go ape**** and maul the babies. They place aggressive weiners in homes with old people without kids around who can dote on them. I didn't believe her, but I have definitely seen aggression with my little weiner dog.
Twice now, he has bared his teeth, growled, snapped, and attempted to bite me when I have repremanded him for something. One time, he took off out of our yard and bolted across the street. My fault for letting him out front off leash, but that's another story. When I picked him up by the scruff of the neck and was telling him my mind, he did actually bit me. Nothing major (no blood), but pissed me off and hurt my feelings

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He glared/growled/snapped at the wife the other day after pissing on our bed when she wouldn't play with him. WTF. With the exception of those three incidents over two years, the best dog, hands down, I've ever owned or been around. Not sure what sets him off exactly, or if he's just trying to assert dominance to challenge us once in a while, but I'm not happy about it.