As a pet and pet/people portrait photographer with decades of experience I pride myself on the ability to capture portrait happenings like this one here.
This of course, was a spontaneous occurrence that happened while I was taking more traditional portraits of the loving dog mom and her dog.
There are ways for me to encourage something like this to happen during the session but no way to know for sure. My camera and lighting system of course are top-notch and I have the fast reaction timing with my camera and right composition to go along with it.
Portraits like this one are a fun and treasured addition to the more traditional and classic portraits I always make it a priority to create. Also, as a side note–her clothing color and my choice of background highlight her Chocolate Lab nicely.