The second is in the back row, shooting the first camera shooting the action. They're almost ready to do it for real. Michael's little dog Augie is getting jealous of the kitty, who has plopped down on top of the on-camera bathmat. Megan, deep breath. Michael breathes deeply.
Action is called, the pratfall is repeated.
The rear camera keeps rolling. Do it again, make it longer. Suddenly, there are pieces of equipment, crew members, actors, and toddling babies underfoot. Filming a movie about filming a movie within a movie. Writing about filming that movie.