I think this song was also featured at the end of the movie Rat Race.

Had to scroll way to far down to find this. Both because how big the song got, and how literally dozens of us watched Mystery Men.

Twice, in fact.

It’s so popular from Shrek [...]

[...] it started in Mystery Men.

I was 15 years old in 1999 when Smash Mouth dropped their second album, "Astro Lounge." All Star was the hit song released on that album and it was all over the radio for the next couple years.

It was an extremely popular single at the time. Everyone in my school would drop everything to sing along if it came on the radio. Most of my friends (myself included) owned the album on CD. And to think the song was written as an afterthought, when they were finished with the album but needed more songs to fill it out a bit.

And yes, Mystery Men (1999) was the first film to prominently feature the song. But that film was technically a flop at the time of release, so most people didn't even see it. Which is why no one knows that All Star was in that movie.

Right as the song's popularity was finally starting to die down, Shrek (2001) released and brought All Star back to life. And it's become the anthem for Shrek movies ever since.

It was an incredibly popular song on its own back in the day. Shrek just ensured it lasted for several generations instead of dying out in the early 2000s.

My kids saw Shrek! not too long ago and got into that song. So I put the video from YouTube up for them and did a double take because I had completely forgotten that the video itself is a tie-in to Mystery Men (which is severely underrated imo)

In what?