Director James Gunn participated in the latest edition of the #QuarantineWatchParty for 2014's Guardians of the Galaxy and revealed the complications that came with including Thanos in the Marvel Cinematic Universe film.
The movie is significant in the MCU's overall storyline by featuring the first appearance of Thanos outside of a post-credits scene, and was used to flesh out his story before he became the focus later down the line. However, Gunn saw the inclusion of Thanos as a challenge. In one of his tweets, the director described Thanos as "an extra complication" for the audience, and was also the most difficult part of the editing process.
Gunn responded to another fan by clarifying that the only thing Marvel asked him to do was include the Mad Titan, and to possibly flesh out the Infinity Stones. Other than those caveats, he was given free rein to do whatever he wanted with the characters.
Directed and co-written by James Gunn, Guardians of the Galaxy stars Chris Pratt, Zoe Saldana, Dave Bautista, Vin Diesel, Bradley Cooper, Lee Pace, Michael Rooker, Karen Gillan, Djimon Hounsou, John C. Reilly, Glenn Close and Benicio del Toro.