So this exists. Dog owners with young dogs can drive to a pet obedience school, and the trainers will let all the puppies run around the compound to play with each other. And it is every bit as adorable as you imagine.
The way I understand it, the point of the whole exercise is to take the puppies fears of other dogs, to socialize them and prepare them for proper training. The trainers obviously advertise courses they offer, but they dish out a healthy dose of free advise and insight, too, so every new dog owner is sure to take home one or two good hints on how to get along with their little runts.
Unfortunately it was freezing cold (I might have lost a toe or two in my steel cap boots there), but the turnout was still really good. All kinds of breeds and sizes were there. The little Shih Tzu in the video is Sanza, my roommates dog. The British Bulldog was awesome, it had already figured out that it would come furthest in life by just sitting down on the other dogs and smiling like a moron, while all the humans go „D’Awwww!“
The tiny dachshund you can see in the vid was the dog that stole my heart in the end though. It wouldn’t stop howling in the beginning because every other dog there was much bigger, and it hid behind peoples feet, tail between the legs. But towards the end of the hour, it was running around with the other dogs, careful, but clearly more relaxed. Beautiful, really.