Alan Gunn’s review published on Letterboxd:
Yeah, you could argue "Popstar" is just a feature-length Lonely Island video, but when these guys are delivering the same consistency of rapid-fire jokes and instantly-catchy songs, it's hard to complain. It's a warped mirror to the face of celebrity culture, poking fun at how the media digests/regurgitates musicians, and while it may go for the obvious gags, it still manages to hit them dead on while having something smart to say. All the fame and excess that come with this lifestyle are explored and exploited to hilarious effect, but there's also a surprisingly touching reminder to never forget your roots and, despite the ups and downs, remember those who have been with you all the way. I guess that's what makes this the best Lonely Island movie you could ask for: for all the celebrity cameos, pop culture satire, and over-the-top production on display, "Popstar" is ultimately all about these three silly guys and them doing what they love.
And yes, I will be buying that soundtrack very very soon.