He's a border collie / blue heeler mix pup, and is nearly 4 months already!
Here's when we first got him, about 8 wks or so old and barely 10 lbs.
This one is closer to 9 weeks I believe. The string around his neck was from his e-collar. My bf's sister in law's vet clinic had a new student who was doing FREE neuters for experience. I thought he was kinda young to be fixed, but we had a hard time passing up free!
This one is near the 3 month mark...
And this was from last week, a whopping 23 lbs!
He's a little doll and is quick as a whip. He was potty trained in only a couple days, and knows sit, down, stay, come, and will play fetch. He's pretty high energy, but not as hyper as I'd expect that mix to be.
That look on his face in the first pic is him whining. When we got him, he was so used to being carried by kids he'd whine every time we'd put him down to walk on his own. It was so cute... but he finally realized he had to walk on his own.
You can see his ear progression, as well. When he's really intent on something, both of those satellites will stick straight up! Most of the time he has one up and one down, though, and looks like a goof.
He doesn't have a tail, either, just a nub. I bet it had a white tip on the end of it, though

. I wish he had a tail, but oh well.