Green Day frontman Billie Joe Armstrong will step into Broadway tuner “American Idiot” for eight perfs beginning Tuesday, making his Main Stem debut in the musical based on the Green Day album.

Armstrong, credited as composer and co-book writer of the show, will play St. Jimmy, the punky alter ego of the protag. The thesp currently playing the part, Tony Vincent, exits the show for two weeks for what reps call a personal family matter.

During the remaining week of Vincent’s absence, understudies Joshua Kobak and Andrew Call will take on the role.

Armstrong’s stint in “Idiot” fell into place thanks to a weeklong opening in the band member’s sked. After appearing on the Rialto, Armstrong will head to Venezuela to kick off Green Day’s South American tour.

Casting of the high-profile rock star could potentially prompt a notable uptick in the show’s box office for the frame, which falls during the traditional September doldrums. Box office so far for the musical has been generally solid but has yet to hit blockbuster numbers.

Armstrong appears in “Idiot” through Oct. 3.