Most notably averted with Lili Cooper (Original Martha), Remy Zaken (Original Thea), and Gideon Glick (Original Ernst), who were all still in high school during the Off-Broadway, and early Broadway run.
Given the vocally and physically demanding roles, the sexually explicit content, and the fact that the main characters are all around 14, this was inevitable. The ultimate examples have to be the 31-year-old Krysta Rodriguez as 14-year-old Ilse, followed by the 29-year-old Andy Mientus playing Hanschen, and the 28-year-old Alex Wyse as Georg.
Averted by Lea Michele in the workshop productions.
Averted by Jennifer Damiano in the original Broadway cast, who was fifteen when the show opened (and was actually supposed to understudy Lea as Wendla until the show found out they couldn't have an actress that young perform in a sex scene.)
Descended Creator: Andy Mientus pitched the concept to Michael Arden and co-directed the initial version. He stepped into the role of Hanschen from the Wallis Annenberg production onwards, because Joey Haro left for a movie and Arden was panicking over being unable to find a replacement in time.
Dyeing for Your Art: Andy Mientus (1st National Tour and Deaf West's Revival Hanschen) had to dye his natural brunet hair blond for the role.
Steffi D (1st National Tour Ilse) had to cut her asymmetrical bob, because one of the producers thought that it looked "too 2008" for the setting of the show.
Hostility on the Set: During the original Broadway run, Lea Michele (Wendla), and Jonathan B Wright (Hanschen) were sleeping together while they were each in other relationships. They were found out, and Lea did something to piss Jonathan off while still on stage, and afterwards he cursed her out backstage with his mic still on. After that, he was suspended and it didn't seem like he mended things because he didn't go to the 7 year reunion back in 2013 with the original cast.
The main cast is played by a bunch of college-aged kids who spend all their time together! This was bound to happen. Numerous pairing have been linked throughout the show, special nod to Christy Altomare (Tour Wendla) and Gerard Canonico (Broadway Moritz) who met through Spring Awakening but were never in the same cast.
In the revival, Andy Mientus (Hanschen) and Michael Arden (the director) were engaged during the revival, and are married as of August 2016. note Granted, they were engaged before the revival was conceptualized...
Miles Barbee (Otto) and Sandra Mae Frank (Wendla) are dating.
Kimiko Glenn (Thea, first national tour) is in a relationship with Sean Grandillo (Voice of Otto). Also, during most of the run of the first national tour, she dated Lucas Wells (Ensemble, and understudy for the male roles).
Matt Shingledecker (Otto, first national tour), and Krystina Alabado (Ensemble, and understudy for the female roles) dated throughout the run of the tour.
Kyle Riabko (Melchior, first national tour), and Steffi D (Ilse, first national tour), dated for a while during the tour.