Will they ever get along?

Yes, they will. If you take off that silly muzzle and allow them to interact! Casper will set his boundaries with Daffy and that will involve a little tussle but just keep an eye on them. I had 2 doxies and a cocker when we received a 3 week old yellow lab a few months ago. One of my doxies was getting increasingly meaner, snapping at other pets and at family members. When he took the helpless, sleeping puppy by the throat and tried to kill it right in front of me, I knew it was time to do something. So I took the doxie to my vet who had watched him attack various pets for 2 years and said some dogs are just wired wrong and with heavy heart, I had my little guy put out of his misery. So, I have seen vicious, mean dogs. Casper is neither. Caspers home and "pack' have changed a bit, he just needs reassurance that he is still loved and wanted. I asked my vet about a muzzle for my little guy and was told it was no way to live and that it would not fix the problem anyways. I sill have that yellow lab puppy, although hes now almost 6 months and is no longer little. My cocker who has water on the brain has established herself as his "mother" and will literally bring him down to her height if he does something she doesn't like and my 8 yr old doxie sometimes wants nothing to do with him and lets him know, but I assure you they all get along fine and there has been no blood shed with these three. Right now as I write this they all all three on the couch, with the cocker cuddled up to the lab and the lab (being in the middle) cleaning the dachshunds ears. It does take time and patience but its worth it. Just let them have time together. Otherwise, they will never know how to interact. And just so you know, Casper hates that muzzle. Give him some special time and extra treats and he and Daffy will be fine together. I do agree that what is seen on that video is frustration, not aggression.

I watched the video, please take the muzzle off of Casper. I didn't see anything that I would call aggression. Older dogs will teach the younger dog the boundries. It looked like Casper was wanting to interact with the pup. I have five grown Boston Terriers, when we have a batch of puppies, those puppies will drive the others nuts wanting to play and romp. I have seen the older dogs mouth the pups, paw at them and knock them around and the pups keep coming back for more, then one of the adults will have enough, give a growl or a snap, and suddenly the pup will just drop down and go on to mess with someone else. I have a 7-year-old chihuahua that will not tolerate the puppies playfulnes at all. When they approach her and start to play, she'll carry on like crazy, snapping, snarling and growling, she has never hurt one, other than it's feelings. Then I want to thump her on the head. The puppy will just drop down submissively and ease off. I feel so sorry for the pup, it's little head will droop, it's ears will droop and it just slinks off. I know the pup is confused, not really sure what it did wrong. And like I said, I want to thump her, but I don't, I just watch them close and let them work out their differences. I believe your little family will be fine. Even if Casper does give the pup a bite, it won't kill it. It has to learn the rules. In a few weeks the pup will be plenty big, then you may have to protect Casper from the playful moose lol.

What I wondered when watching that video was, where were you allowing that to happen? To have a young puppy pestering a muzzled adult dog can eventually lead to real aggression. That was nothing more than your spitz wanting the pup to go away, not aggression. I just don't see why you allowed the pup to continue? What for? If you want them to sort it out on their own, then remove the muzzle and let the spitz have a chance of disciplining the puppy. He won't hurt her, just show her what is acceptable and what is not. If you do not want him to do the discipline, then you have to do it for him as with that muzzle on he can't. Anyway, my puppy was just the same as your Daffy when growing up. My aunt had an adult golden retriever who we dogsat every day while she was at work who didn't tolerate my pup at all as he was much too boisterous and just wanted to play. We kept them separated with babygates for closer to a year, and once my pup grew out of the first mad puppy year and was trained to know how to approach other dogs, they became best friends. But there's been a lot of work involved and a lot of supervision. We couldn't even leave them together in the same room while we were in the room with them, much less alone.

They are not into hurting each other infact I see them as enjoying each other don't worry if casper is irritated now he will get use to it.