The singer and Broadway actor is one of the soda brand's newest mascots, Lil' Sweet. He's a tiny little glam-rocker with a voice as sweet as substitute sugar.
And somehow that has something to do with Diet Dr. Pepper. Look, don't think too much about it, just enjoy Justin's hilarious work as Lil' Sweet.
Here, Lil' Sweet brings some co-workers some much-needed soda in a workplace. We also learn that Lil' Sweet is self-employed.
Here, Lil' Sweet brings some Diet Dr. Pepper joy into the life of some guys at a kid's birthday party who can't enjoy any of the cupcakes because they're watching their weight. We also learn that Lil' Sweet can defy gravity.
Will Lil' Sweet be the next Geico Gecko or Flo from Progressive Insurance? It's too soon to tell, but you've got to admit that Justin actually looks pretty awesome as a wannabe member of Warrant.
It's nice to see Guarini bounce back from some tough times the actor admitted to having a few years ago. In 2013, the singer actually sat down with Oprah, where he revealed that his fame from "American Idol" may have helped his career, but it damaged his life.
Guarini isn't the only actor starring as a strange, surreal spokesman in a commercial. Rob Lowe has been appearing as many bizarre characters for DirecTV. Check out a behind-the-scenes look at one of the hilarious ads in the video below.