We should all hail Green Day, the first punk rock band to come to Broadway. Except, before we all cheer, I want to note that Green Day is not actually coming to Broadway. I point this out because I think people will be confused. And I don't blame them.
For those who need a little background (like theater journalist Patrick Pacheco, who recently stated that he had never heard of Green Day), American Idiot was the name of Green Day's 2004 rock opera recording. The songs followed the story of a character named Jesus of Suburbia as he watched his American dream slip away. American Idiot sold tons of copies and won a Grammy for Best Rock Album. 
Now it is a stage musical. Green Day's singer and lyricist Billie Joe Armstrong collaborated with Broadway director Michael Mayer on the book. Featuring all the American Idiot songs plus other Green Day tunes, the musical premiered at California's Berkeley Repertory Theater and will soon begin performances on Broadway.
The art for the Broadway production is the album cover art. The cast performed with Green Day on the Grammy Awards. The production also released a video for the song "21 Guns" with the stage cast and the band. In the video, Armstrong is seen providing vocals as if he was just another cast member. But he's not. He is not in the show. None of the members of Green Day are in the show. And I wonder when people will find that out, before or after ticket purchase. The opportunity for confusion is so great that Berkeley Rep promoted the show with this disclaimer: "This is not a Green Day concert--this is the stage version of American Idiot developed by Green Day and Michael Mayer. Although the band will not appear on stage, the show will definitely rock." The Broadway production has not done anything of the sort. Do they want people to purchase tickets thinking they are seeing Green Day?
One could argue that it is not the production's responsibility to clear up all misconceptions that ticket buyers might have. After all, caveat emptor. It is really just the production's job not to affirmatively mislead--to not say in the ads that Green Day is in the show. (The ads, of course, make no such claim.) That is true. It is also true that a musical is not going to play as well when a quarter of the audience is waiting for Billie Joe Armstrong to appear.
Huge fans of Green Day will indeed know their band isn't appearing, they will buy tickets to hear the music in a new way. Older people (ala Pacheco) may not know who Green Day is and will not care if they are present at the St. James Theater. It is the individuals in the middle I worry about. Those who know a little about Green Day, see the art and think: "Green Day on Broadway? I so need to take my [insert loved one here]."
This is not the first time a show has created such confusion. There are always going to be people who are simply not savvy when it comes to these things. People thought Billy Joel was in Movin' Out. Maybe people think ABBA is in Mamma Mia!. I don't know. But one must think back to The Who's Tommy to really recall a situation similar to American Idiot. (Armstrong frequently cited The Who as an inspiration for the album in the first place.) The Who's Tommy was another album-turned-musical heavily associated with the band that conceived of it, as evidenced by the show's official name being The Who's Tommy, as opposed to merely Tommy. Notably though, the production artwork was completely different from that of the recording. No existing Who images were used in promotion. While Pete Townshend did help publicize the show, he never publicly performed with the cast. It was different. It was less misleading. Did some people arrive at the St. James Theatre expecting to see The Who? Probably. But what I'm discussing is a matter of degree.
Last night, at dinner, someone said to me that they think it is funny that people are going to buy tickets thinking they are seeing Green Day. You could certainly make jokes along the lines of: "Those people are really American idiots!" I would not laugh however. Well, maybe I would, but then I'd think about how annoying those audience members have the potential to become.