- Disabled Character, Disabled Actor: Christopher Diaz has cerebral palsy. He is played by Gavin McHugh, who also has cerebral palsy.
- Fake American: Oliver Stark (Buck) is British.
- Meaningful Release Date: Season 4's premiere date is scheduled for January 18th, which can be abbreviated to 1/18, which also happens to be the number of the firehouse the show revolves around. The show's social media takes advantage of this, saying that "the 118 returns on 1/18."
- Real-Life Relative: Maddie's abusive husband Doug is played by Jennifer Love Hewitt's real-life husband, Brian Hallisay
Trivia / 9-1-1