- Nathan Fillion is one of the actors who have portrayed multiple characters in the Marvel Cinematic Universe.
- Nathan Fillion previously worked with James Gunn in Slither and Super, and with Joss Whedon in Firefly, Buffy the Vampire Slayer, Dr. Horrible's Sing-Along Blog and Much Ado About Nothing.
- Nathan Fillion previously dated his Guardians of the Galaxy co-star Mikaela Hoover.
- Nathan Fillion was in talks to play Hank Pym in The Avengers before it was decided that Pym would not appear in the film.
- Nathan Fillion voiced the Green Lantern Hal Jordan in the DC Universe Animated Original Movies Green Lantern: Emerald Knights, Justice League: Doom, Justice League: The Flashpoint Paradox and Justice League: Throne of Atlantis.