Smash Mouth’s Steve Harwell thought ‘All Star’ could be big. ‘Shrek’ made it an earworm.

“What the f— is this?” Harwell had asked, he later recalled to Rolling Stone.

The song would eventually be known as “All Star,” the surprise 1999 hit that served as a radio-friendly pop-rock anthem for outcasts and that put the San Jose band on charts around the world.

“I just knew right away — this thing’s going to be everywhere. It’s going to be played at every basketball game, hockey game,” Harwell recalled to Boston radio station WBUR in 2018. “You’re going to hear ‘All Star’ — just like you always hear ‘Hells Bells’ or ‘Back in Black.’”

But “All Star” earned earworm status two years after its release not because of the arenas and stadiums it was played in. Instead, the song soared to new heights when it was featured in the opening of “Shrek,” the 2001 animated comedy about an embittered ogre whose swamp home has become overrun by fairy-tale creatures banished by an obsessive ruler. The boost “All Star” got from “Shrek” would later turn Smash Mouth’s biggest song into a staple of internet meme culture in the 2010s, making it forever inescapable.

“We had no clue how big ‘Shrek’ was going to be. We had no clue,” Harwell told Rolling Stone in 2019, adding: “The song was reborn again.”

Sharp. Witty. Thoughtful. Sign up for the Style Memo newsletter.

Harwell died Monday at 56. The band’s manager, Robert Hayes, confirmed Harwell’s passing, which occurred at the singer’s home in Boise, Idaho, in a statement to media outlets and a Facebook post.

Harwell had liver failure and was resting at home while being cared for by his fiancée, Hayes said Sunday, adding: “We would hope people would respect Steve and his family’s privacy during this difficult time.” Harwell announced his retirement in October 2021 to focus on his physical and mental health after a performance in Upstate New York, videos of which show him in an apparently disoriented state. He struggled with addiction over the years, leading to health complications, including cardiomyopathy, which results from a weakening of the heart muscle, that affected his speech and memory, Hayes said.

“Steve Harwell was a true American Original. A larger than life character who shot up into the sky like a Roman candle,” Smash Mouth wrote on X, formerly known as Twitter. “Steve will be remembered for his unwavering focus and impassioned determination to reach the heights of pop stardom.” The band still tours, with Zach Goode as its lead vocalist.

Although Smash Mouth found success in its 1997 debut album, “Fush Yu Mang,” critics wondered whether “Walkin’ on the Sun” would leave the band as a one-hit wonder. At the completion of the group’s second album, “Astro Lounge,” executives at Interscope Records told Greg Camp, the band’s primary songwriter and guitarist, that what Smash Mouth had given the label wasn’t marketable.

“They’re just like, ‘Where’s the hit?’” Camp recalled to WBUR. “‘This isn’t it. You got a second single. You got a third single. Maybe a fourth single. But not a first single. We’re not gonna put this out until you give us something better than this.’”

Camp picked up a Billboard magazine and was forced to ask himself a question he hadn’t had to ask before: “What do people listen to these days?” As he started to write, he thought of all the fan mail the band had received from young people who said they were being bullied. Some were picked on for how they dressed, others for simply liking Smash Mouth.

“We were reading a lot of fan mail, back when people actually wrote things on paper,” Camp told NPR in 2018. “We were reading all these things, and we were like: ‘Man, all these kids had or are having the same problems that we had when we were kids. Let’s do a song.’”

With his mission in mind, Camp wondered what the song’s title could be. That’s when he looked down at the shoes he was wearing — Converse All Stars — and knew what the song would be called. Keyboardist Michael Klooster recounted to VoicesRiverCity.com in 2017 about how Camp had told his band members about how he had been working on two new songs.

“I remember talking to him, he goes, … ‘There’s one I really like. One I kind of hate, but I think it’s gonna work,’” Klooster said, referring to “All Star.”

Harwell heard the demo tape Camp had put together and knew he could turn it into a Smash Mouth song — the Smash Mouth song.

“I’m not going to toot my own horn, but nobody else could have sang that song. It would have never been what it is now,” Harwell said in 2019. “I could’ve pitched that song to a million bands and they would have tried to do it, and it would’ve never been what it is.”

Hailed by critics as “the perfect summer anthem,” Smash Mouth’s “All Star” was seemingly everywhere after it was released in May 1999: the tops of charts, venues across the country, Major League Baseball’s Home Run Derby, the Grammy Awards.

“I just said at one point, ‘I think this song will definitely do what the record company wants it to do, but you may potentially fly your band straight into the sun with this song,’” producer Eric Valentine recalled to WBUR. “Because there’s no turning back from this.”

Though “All Star” had appeared in several film soundtracks, Jeffrey Katzenberg, then the CEO of DreamWorks Animation, had a suggestion for what he wanted to be played over the opening of “Shrek.”

“Why don’t you just use ‘All Star’?” Katzenberg asked composer Matt Mahaffey, who worked on “Shrek,” according to the Ringer.

Even though Mahaffey initially did not want to use a song that was a couple of years old and that was featured in other movies, the decision paid off. The choice to license the song to “Shrek,” which grossed nearly $500 million worldwide, was part of Hayes’s strategy to make “All Star” as unavoidable as possible in everyday life.

“I licensed the crap out of that song,” the manager told Rolling Stone. “You could not walk into a grocery store or turn on the television without hearing ‘All Star.’ It was very, very saturated.”

Years after the height of the song’s success, the first lines of “All Star” were morphed into a meme machine of YouTube posters remixing the 1999 hit for their own comedic purposes. Among the most popular is a version of “All Star” in which Harwell is singing “somebody” over and over again.

Harwell said in recent years that the band had embraced its status as meme influencers, acknowledging that he and the other bandmates had accepted “All Star” as their legacy.

“At first it was weird, and we were a bit guarded and resistant,” Harwell said to Polygon in 2017 about the memes. “But as we dove into it more and focused on it we started ‘getting it.’”

The Smash Mouth frontman had said he was lucky that the band made “one of those songs” that people can’t get away from.

After Harwell’s death was announced Monday, the YouTube user who posted the “somebody” meme video updated the caption to honor the Smash Mouth singer: “Thanks for singing the greatest song ever made.”