The Pups' Picnic is a MGM Happy Harmonies cartoon, released in 1936.
Two puppies at a picnic are scolded for nosing around the food. They wander off and stumble on a fox hunt, spotting the fox after all of the big dogs have sped ahead. The wily fox then stumbles on the two pups. The chase is on. At the very end, the pups get back in the 1930s car (along with the fox in the wheel of the spare on the back!).