First off, the whole thing is animated -- so all those celeb cameos we've been hearing about are vocal cameos, as the slew of A-list stars lend their voices to everything from wild animals to livestock to even marijuana plants.
Second of all, the whole song is for a good cause! While the lyrics might be profane and hilariously juvenile in parts (and strangely sad and contemplative in other moments), the message of the song is about the importance of working together to help the environmental crisis.
Third of all, there are way, way more big name artists who lent their voices to this song than many people anticipated.
Joining Bieber (who plays a baboon) are Ariana Grande (as a Zebra), Halsey (as a baby lion who eats Grande's Zeba), Snoop Dogg (as the aformentioned marijuana plant, obviously) and a slew of other stars including Zac Brown, Brendon Urie, Hailee Steinfeld, Wiz Khalifa, Adam Levine, Shawn Mendes, Charlie Puth, SIA, Miley Cyrus, Lil Jon, Rita Ora, Miguel, Katy Perry, Ed Sheeran, Meghan Trainor, John Legend, Backstreet Boys and Bad Bunny, among others.
The only animated human characters are Lil Dicky and Kanye West (voiced by Kevin Hart, not West), as well as a truly surprising cameo from Leonardo DiCaprio who actually does contribute a line of dialog at the very end.