"Sharknado." The TV so unabashedly bad that it reminded us of a "B" comedy from the '80s that was pitched to theatergoers with the following tag line. If you see only one movie this year, see this one... See More
"Sharknado." The TV so unabashedly bad that it reminded us of a "B" comedy from the '80s that was pitched to theatergoers with the following tag line. If you see only one movie this year, see this one also. Why has "Sharknado," a film of a sealess celebrities battling sharks become such a phenomenon? Here's nick watt. Reporter: It's the most unlikely plot in history. There's sharks in the street. Reporter: A tornado scooping man-eating sharks out of the ocean. Domping them on L.A. It's something that a 6-year-old kid would come up with. Exact flip. Reporter: Even more unlikely, the outcome. That movie was so successful, they made a sequel. "Sharknado 2." The same thing happens, this time in New York. The big apple. Something bites us, we bite back. Here's a formula. It worked in the first one. We don't want to mess with that one. Reporter: Tara Reid is back for more. Better than the first? In my opinion, yes. Reporter: Ryan ziering is also back. They're sharks. They're scary. No one wants to get eaten. Reporter: The chain saw comes back. What he does with it is going to be the fun part. Let's go kill some sharks. It's happening again. It's really one of the shark storms here? Yes. Reporter: It doesn't really make sense. It doesn't. But that's "Sharknado." Reporter: The first movie, so bad that it's good. Generated 5,000 tweets a minute. Social media is almost the reason for existence of a movie like this. Reporter: He's one of the cameos in the sequel. Is Billy ray Cyrus in this? Yes. Billy ray's in the movie. Reporter: What's he doing? He plays a doctor. Reporter: Other cameos include Kelly Osbourne. They were lining up. But the first movie, they had to lie to get anyone involved. Are you okay? My mom always told me Hollywood would kill me. Reporter: In the beginning, it was called "Dark sky." I thought, okay. Doesn't sound so bad. And then, like, three days into the movie, they started calling it "Sharknado." We can't call it "Sharknado." It's going to look horrible on my resume. I'm going to never work again. I said, trust me. They call it "Sharknado," it's going to be a good thing. When the movie came out, I was in Mexico. And the next day, I was on a plane back to L.A. And the stewardess came up to me and said, I love "Sharknado." What are you talking about? It got me out of being the girl from "American pie." And I'm in "Sharknado." Reporter: "Sharknado 2" premieres tomorrow night in 90 countries. "Sharknado 3" is in the pipeline. As Vanessa Williams once said, isn't this world a crazy place. Let the fireworks begin. Reporter: I'm nick watt for "Nightline." Wholly shark. Reporter: In Los Angeles.
This transcript has been automatically generated and may not be 100% accurate.