Context: In The Avengers (2012) Thanos makes a cameo appearance in the middle of the end credits. Damion Poitier (credited as Man # 1) portrays Thanos as Loki's mysterious benefactor. In Guardians of the Galaxy (2014) Thanos tries to use Ronan the Accuser to obtain an Infinity Stone. The film also introduces him as the adoptive father of Gamora and Nebula. Sean Gunn stood in for Thanos on set. Josh Brolin provided the performance capture for Thanos. Thanos was originally going to have a larger role in Guardians of the Galaxy, but Joss Whedon felt that the character needed to be threaded more gently. In Avengers: Age of Ultron (2015), Thanos makes a cameo appearance in the middle of the end credits. He dons an Infinity Gauntlet and vows to retrieve the Infinity Stones himself. Brolin reprises his uncredited role. In Avengers: Infinity War (2018), Thanos is once again portrayed by Brolin. In the film, he seeks the six Infinity Stones because he believes the Universe is overpopulated and wants to cull it by half so that those who remain may have a better quality of life. Brolin will reprise his role in the fourth Avengers movie (scheduled US release, May 3, 2019).\n\nQuestion: what was the first movie thanos was in? Let's have some stream of consciousness first.
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To answer the question, consider the following: In The Avengers (2012) Thanos makes a cameo appearance in the middle of the end credits. So, the answer is The Avengers ( 2012 ).
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