I find that the swimming animation of dogs is made incredibly well. A detail that has me smiling whenever I see it. Active dogs will use a home pool often. Did you know that your Sim can throw a ball into the water and the dog will swim to fetch it? Also, on the beaches in Sulani, dogs will head out to swim - it's really enjoyable and fun to watch a Sim swim with their dog :)
Also, the faces of both cats and dogs are incredibly expressive - another detail I really appreciate and which speaks of care and effort on the developer's part.
@Paigeisin5 I recall seeing the same scenario in a save once. It's rather comical, and I do believe dogs are meant to growl at aliens in disguise as a sign that they can't be fooled - like a tribute to their fabulous noses ;) I have also had pets that just didn't seem to really get along no matter what I tried, while others become bffs.