Popular Science notes that when you look at corgi mixes, the dogs tend to look like the other dog breed with the usual proportions, but then with shorter legs.
There's a genetic rationale for this doggie cuteness — they've inherited achondroplastic dwarfism from their corgi parent, PopSci adds.
The first dogs with short legs cropped up randomly about 300 years ago, it notes, with breeders then deliberately passing the trait along.
As PopSci writes, corgis have a mutation in fibroblast growth factor 4 (FDF4) that leads the dogs with have one copy to have shorter-than-usual legs. Dogs with two copies of the FDF4 variant have even shorter legs. As corgis have been around so long, Popular Science says nearly all have two copies of the FDF4 variant, so any corgi mix then winds up with short legs.
Popular Science adds that this effect can also been seen with basset hounds and dachshunds, which also have achondroplasia.