Literally, a Dog and Pony show. The expression once referred to acts held outside a carnival or sideshow. It now means to confuse a someone into thinking a product is necessary or improved, to bamboozle the client. There are more advertising executives than carnival acts these days, but both promise more for your money. (Though this young woman probably took more pride in her work than the folks on Madison Avenue) By the way, the term "dog trainer" (as any trainer will tell you) is a complete misnomer. Dog Trainers train dog OWNERS. Dogs are pretty much born knowing what to do.
"Dog Act and Trainer" Original snapshot c. 1958 Collection Jim Linderman