Oliver Stark, who portrays Buck on “9-1-1,” added to fan theories when he posted a picture of himself hanging out with the cast of “9-1-1: Nashville” on his Instagram story Oct. 6 and encouraged fans to watch the spinoff. McVey reshared the photo on his Instagram story and added, “Come back soon brotha.”

For exclusive news and updates, subscribe to our 9-1-1 Newsletter: 9-1-1’s far-fetched plots are reaching new heights — literally. In Season 9, Athena (Angela Bassett) and Hen (Aisha Hinds) will go from first responders to some of the first civilians in space.