Not every ad is for just one product — or even those of just one company. No, high-profile movies will always attract companies looking to cash in on it. Or, sometimes, two companies are just trying to keep costs down (TV time's expensive), perhaps because neither company could afford to advertise on its own. For whatever reason, you end up with a Dualvertisement: a Crossover in adspace. More formally known as Cross Promotion, this trope's been in existence for at least as long as McDonald's has been giving away licensed toys.
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 (demonstrating that a cheap product is so high-quality that it could pass for its pricier counterparts), where you open with one product then bring in the actual product later to show up the first one.
