Iain De Caestecker portrayed Leo Fitz in Agents of S.H.I.E.L.D. and in the Agents of S.H.I.E.L.D.: Slingshot episode Progress. He also portrayed Fitz's Life-Model Decoy in The Man Behind the Shield and Self Control.
He portrayed himself in Agents of S.H.I.E.L.D.: Academy.
- He was named TVLine's "Performer of the Week" for his acting in the episode Laws of Nature.
- Leo Fitz's obsession with monkeys was inspired by Iain De Caestecker's own love for monkeys.
- Iain De Caestecker voiced an alternate version of Leo Fitz in Ultimate Spider-Man alongside Elizabeth Henstridge, who also voiced an alternate version of Jemma Simmons.
- Iain De Caestecker shares his birthday with Jude Law, Kevin Weisman and Dylan Minnette.