A single commercial advertises two things at once
Most commercials advertise a single product, it helps keeps focus on one thing and you have plenty of time to get your message across. But sometimes that's not enough for the marketing department. I mean, wouldn't that restaurant commercial be twice as interesting with a character from that new movie? And the viewers will have double the urge to buy things! And you only have to film one commercial and pay for one timeslot! Everybody wins! While this has some pros, the cons often outweigh them; rarely do the two items/shows/etc. mesh, and the commercial can end up less interesting and more surreal as a result, or even result in straight up Fridge Logic. Often a part of a larger promotion/marketing campaign, since it takes a lot of effort for two companies to get together. Compare Commercial Switcheroo, where you lead in with a fake commercial then bring in the real one, and Product Switcheroo Ad, where you open with one product then bring in the actual product later to show up the first one.