The manga artist, Hajime Isayama, got the idea for the Titans when he encountered a drunk customer at a coffee shop he worked in. He was inspired by the inability to communicate and realised the most dangerous thing was the human race.
In both the anime and the manga, the Titans appear completely naked, though this isn't all that offensive since they are portrayed as not having any sexual organs. However, due to censorship laws, the Malaysian version of manga portrays the Titans as wearing pants.
Aspects of Levi's design and personality were based on Rorschach from Watchmen.
Isayama has been vocal for his love of shows like Game of Thrones and Breaking Bad. He even revealed that Falco Grice is based on Jesse Pinkman, played by Aaron Paul. The show's Saul Goodman, as well as many Game of Thrones characters even made "cameos" in the manga where they appeared as Titans.
MAPPA studio took over production for the final season when producers had wanted to take the production to another studio by the third season. Producers Toshihiro Maeda and Kensuke Tateishi said they shopped around but most studios weren't up to their standards or declined due to the expected work volume except for MAPPA who responded with a "we'll think about it." The people at WIT Studio whom had produced the show since 2013 have reportedly said they're comfortable with MAPPA taking over production.