One day, Mabel had been begging and begging for a cat or a dog to Stanley and Ford, Dipper had decided to join in and they both literally begged for a puppy, and eventually Stanley gave in, pretty quickly, but Ford held up in bit getting one, but eventually he gave up and gave in to the begging, so later that day, the Pines went to a pet store, Ford grumbling the entire way but softened up a bit, they all agreed to a puppy, so they went into the store, and started looking around, they couldn't find one so they asked an employee

Mabel: "Hey, do you have an dogs?"

Employee (Jack): "Yes we do, they're over here"

He would lead them to the left side of the store to show many dogs

Ford: "Any well trained dogs?"

Employee: "Yes, we have quite a few, but if you want a well trained AND intelligent dog, this is the one for you"

He would show them to your cage