Having an ad go viral can be an amazing boost to your marketing. Just Alexandria Ocasio-Cortez, whose The Courage to Change video. Brilliant storytelling that helped her get elected to Congress. And then there are the many attempts to go viral that never work because it's a lot harder than it seems, no matter how good your work has been.

But what if you had an ad that went viral because it didn't make much of any sense? That's our case study today. Before anything else, watch it below. If you start getting bored, it's okay to watch part and then head to the end (although seeing the whole thing is helpful).

Who would have thought? As AdAge noted, it's a three-year-old ad that was originally intended for the Brazilian market. An arty short that's supposed to be an ad for Subway.

The message: You're born, raised, grow up, experience life, heartbreak, and you end up eating a sub sandwich.

Advertising is a tricky thing. There's a general split between direct response ads that are supposed to get you to take an action and a brand or image ad.

The first type treats actions as part of a purchase "journey"ؙ--as many people in marketing, particularly those employed at agencies, now call it-- Maybe you get to charge more that way?

Okay, seriously, there is a journey in the specialized and limited sense that someone may have a need, or be receptive to being convinced into having one, and then do the research, comparison, and eventually the purchase. Sometimes it's really fast, like you're hungry and need a bit to eat so what are you in the mood for today, or it can take much longer: buying a car, a house, a vacation destination.

Then there are the brand or image ads. These are trickier because the intent is longer in scope. You can't see a direct correlation between the marketing message and an ultimate purchase. All you can hope for is to build the brand--in all its often ephemeral forms--and presume that it will stick to the people who could have the biggest affinity to it and your company.

This is readying the ground for a long-term relationship so that when people want the type of product or services your company offers, they turn to you.

Except that means you need some kind of solid connection between the ad message and the brand. Many companies have been good at this, often through humor in the fast food sector. Like the KFC chicken corsage ad. Droll.

Where ads, and, again, particularly in the fast food segment, often fail is when they try to be heartwarming. Like the U.K. McDonald's ad about a kid growing up who, the more he hears about what his father was like, the more distant he feels. Until his mother mentions that they both liked McDonald's fish sandwiches.

That was ridiculous. The Subway ad is ... just crazy. Your entire life is spent so you can order a sandwich? There's nothing inherently connected to Subway, which more often uses either humor or a more mundane appeal to hunger and monetary savings. That's why the appearance at the end has left so many people scratching their heads and saying, "Huh?"

I mentioned two types of ads. There's actually third: the type agencies put together to win awards and feel good about themselves. This one seems to have fallen into the third camp. But in such a strange and awkward way that got 2.4 million views in a day. Three years after it was created.

Sometimes the marketing deities smile and pour forth the benefits. When they do, it's best to be ready, with something that doesn't leave the public wondering what the hell you were thinking.