My sims' dogs, a pair of downloaded customs, had a litter of puppies, one of which I adopted out to the sims' son on another lot and the pup just grew up...deformed. A bit odd looking I wouldn't mind, but while I know it can't happen I'm almost afraid that the weight of his head might break his long, skinny neck! No idea where that came from as the parents were the same breed and similar in structure.

I know that there's several hacks and the Plastic Surgery Machine from Uni for modifying the facial structure of human Sims, but is there anything similar for modifying the body structure of Pets? I haven't been able to find anything and it's only possible to change their coat in the mirror.

I'm also looking for a such mod :с
When I try to put on the collar through the mirror, the tail's fur disappears. But the tail cannot be changed through the mirror

I've changed the whole appearance of a dog in the mirror when I didn't like the way it grew up. But that was picking a breed to have it look like. Do you just want to change the neck?