Former "Saturday Night Live" star Andy Samberg and the Lonely Island guys take to the big screen this weekend with faux-music documentary "Popstar: Never Stop Never Stopping," and the film — which opens Friday — is getting solidly mediocre reviews. But there's one element that truly elevates the film: An epic list of celebrity cameos.

The stars who show up are too numerous to name, but to start: Questlove, Carrie Underwood, Nas, 50 Cent, Ringo Starr, Simon Cowell, Adam Levine, Pink, Emma Stone, DJ Khaled, A$AP Rocky, Mario Lopez, Pharrell, Jimmy Fallon, Martin Sheen, Snoop Dogg and more.

With so many celebrities making an appearance, some playing themselves and some playing an odd list of characters, which ones are the best? Spoilers abound, but we think that five of them tied for the top spot.

1) Mariah Carey

It's a shame the Lonely Island trio couldn't get Carey to sign up for a song on the truly bizarre soundtrack, but the pop diva gets in a couple of the film's funniest lines as one of the celebrities interviewed for the doc about pop star Conner4Real's (Samberg) life. Speaking about "I'm So Humble," a ridiculously catchy track that Conner sings with Adam Levine, Carey admits she relates to the message. "I really connected with that, because I'm the most humble person I know," deadpans Carey, who famously played a live version of her hit "Fantasy" as she gave birth to her twin babies "so they could hear the applause as they entered the world."

2) Will Arnett

Arnett plays an excellent takeoff on TMZ founder Harvey Levin in his syndicated show "TMZ on TV." In the "Popstar" universe, there's a celebrity "news" show called "CMZ." As the "CMZ" ringleader, Arnett boasts Levin's signature T-shirts and a cup in hand (an entire pitcher at one point) as he holds court in a newsroom with his gang of reporters who find all their own jokes hilarious.

3) Usher

In the movie, Usher earnestly makes another startling confession: His stellar dance skills are all inspired by the "Donkey Roll," a really cool move coined by Conner and his buddies when they were all members of their original band, the Style Boyz.

4) Justin Timberlake 

Of course Timberlake, a Lonely Island collaborator, shows up — though as a super-creepy personal chef who makes all kind of creations with carrots. Spoiler alert: He appears at the end of the movie as a fish playing guitar, which is exactly what it sounds like.

5) Seal

The always-good-sport Seal suffers a brutal attack in "Popstar," as he's trying to provide a beautiful song as the background to Conner's proposal to his girlfriend, Ashley Wednesday (Imogen Poots). It's not his fault that Conner hired wolves as additional entertainment. Anyway, Seal gets his revenge as he sues Conner for the wolf attack and ends up hooking up with Ashley Wednesday.

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