US procedural drama 9-1-1 is set to give firefighter Evan "Buck" Buckley (Oliver Stark) a significant character development, as he agrees to foster a boy named Theo in the Season 9 finale. According to Collider, the move marks a meaningful shift for a character who, despite maturing since his reckless early days, has largely stayed the same across the show's run. The decision continues the ABC series' recent willingness to take risks with its long-running characters.

The article frames this within the show's broader trajectory as it heads towards its tenth season, noting that the biggest recent risk was killing off Captain Bobby Nash (Peter Krause) in Season 8, which permanently reshaped the core team. It observes that Buck has previously been used for lighter storylines — becoming a maths genius in Season 6 and accidentally dating a pair of siblings in Season 9 — but has recently stepped up by helping his crew grieve Bobby and building a healthier friendship with best friend Eddie Diaz (Ryan Guzman). Taking on fostering Theo is presented as a genuine, lasting evolution for the character.