The actor has served as the special guest of the night twice before, but it has been a while.
The 23-year-old Ronan can now be seen in the Greta Gerwig-directed Lady Bird, which hit theaters in early November. Dave Grohl of Foo Fighters has been the musical guest on SNL more times than any other person, appearing 11 times between Nirvana and his current group.More news: Lennie James On Joining The Cast Of 'Fear The Walking Dead'
Franco will be joined by musical guest SZA, the recording artist whose album "Ctrl" debuted at #3 on the Billboard 200 chart and has been certified gold by the Recording Industry Association of America. The R&B songstress released her first studio album back in June, which included a number of songs that reached the top of the Billboard charts. The next week, 2017's breakout star SZA will make her SNL debut in a show hosted by The Disaster Artist's James Franco.
Set to air on December 16, the final "SNL" of 2017 will feature host Kevin Hart and musical guest Foo Fighters.